Positive experience with ACC on Phenom II

[mattkosem]

So, I've read over and over again that ACC doesn't do anything on Phenom II chips. Blocking out all of those bad thoughts, I decided to give it a try...

The problem: Core 3 on my PII 940 does not clock over 3.5Ghz

Research to discover the problem: Setting each core to 3.7Ghz via AOD, one by one then running Prime95 64-bit set to 8k FFTs with 1600MB of ram allocated.

Core 0: No problem
Core 1: No problem
Core 2: No problem
Core 3: Cannot even get into prime before the system reboots.

Attempted solutions:
1) more vcore - no luck
2) lower memory ratio - no luck
3) lower overall clock - lame, but works
4) *ACC

I started by setting ACC to 0% on all but core 3, which I set to +2%. I rebooted the system, and set the clock. Hmm...Interesting...I can set that clock without almost instantly rebooting. So I thinks to myself, this seems promising. I kick off prime, it runs for a few seconds then reboots. Feeling a bit more lucky, I decided to kick it up another notch to 4%. Whadya know, I've gotten through 10 passes of this test without any issues so far.

Did the optimizations for ACC in recent bios revisions do something for ACC that does actually make it effective?

--Matt

[leoy]

Maybe your chip needed the acc. :rolleyes:
If it works for you , then you are ok, don't mind for others.

[crazydiamond]

acc worked wonders on my 9850 but my board wont post w/ acc on auto with my 940

[mattkosem]

Maybe your chip needed the acc. :rolleyes:
If it works for you , then you are ok, don't mind for others.

Yes, you really seem to believe me :rolleyes:. It certainly makes a marked improvement from what I'm seeing now. There's, obviously, quite a big difference between instantly rebooting and being able to prime with the most stressful test that I've been able to muster so far at a given clock. I feel like this mobo is junk, and have a M4A39 Deluxe on the way to replace it. Perhaps the new mobo won't need it, but this one most certainly benefits from it.

--Matt

[leoy]

Yes, you really seem to believe me :rolleyes:. It certainly makes a marked improvement from what I'm seeing now. There's, obviously, quite a big difference between instantly rebooting and being able to prime with the most stressful test that I've been able to muster so far at a given clock. I feel like this mobo is junk, and have a M4A39 Deluxe on the way to replace it. Perhaps the new mobo won't need it, but this one most certainly benefits from it.

--Matt

I would certainly bet on a new mobo....

[richierich]

For some strange reason when I turn on ACC CPUID Hardware Monitor can't detect my CPU temps

[mattkosem]

Believe what you like. I'll enjoy the benefits. It looks like 2% and 1.55v is the best combo for me. 4% and 1.55v doesn't get as far.
--Matt

[Veedo]

i was going to try the same thing on my x3 720. i have one core that will not boot into windows at stock clock, but with a lower multi it will np. this might help!

[mattkosem]

It couldn't hurt to give it a shot. What have you got to lose?

--Matt

[i found nemo]

i was going to try the same thing on my x3 720. i have one core that will not boot into windows at stock clock, but with a lower multi it will np. this might help!

then you should return it to amd ....

[Oese]

then you should return it to amd ....

i think he is meaning the fourth ;)

[Veedo]

yes i mean the freebie core :D. so far i have the other 3 at 3.5ghz running occt. hope to get a bit more, but we shall see!

[i found nemo]

he said stock so i assumed he was using it as x3 still, but idk wich one he means.

edit =

ahhh i c. well in that case more voltagess! lol

[G0ldBr1ck]

ACC does some tricky things with the voltages that may be the key to what your getting.

[mattkosem]

Hopefully I won't have to deal with it when the M4A79 Deluxe comes. It looks like a much better board overall. I only have this one because it was the only one locally available when my other board died.

--Matt

[Throwed]

I have a Foxconn board that has SB750, a Biostar that has SB600, and a ASUS that has SB700. Out of three the ASUs overclocks the best. ACC does nada for my PII 940. In fact, when enabled it makes things screwy so I don't even deal with it. The SB700 suits my taste and is ALOT more stable. Some love ACC and some don't. IIRC, ACC was really just ment for the 1st Phenoms and I am beginning to believe it because I fair no better/worse on the SB750 vs SB700.

[mattkosem]

In my situation, where one core lags terribly behind the other three, ACC on the slow core seems to have bridged the gap. I obviously can't prove to any of you non-believers that the system crashes immediately after setting 3.7Ghz without it enabled on that core, but I've shown that it runs under Prime with it enabled.

--Matt

[AliG]

just a word of advice, don't bother running prime for more than half an hour. I say this because all prime does is torture the cpu, how many times a day do you think you'll be literally torturing your cpu with average load? Priming too long will infact cause some unnecessary damage to the cpu, unless you have some killer cooling, but I wouldn't trust a TRUE for that.

I would use OCCT and if it passes more than ten minutes, you're set (people have found that OCCT will cause errors in just a few minutes while it takes prime95 hours to do so). Just a word of advice, since I was totally into prime95 stability testing myself and now my cpu doesn't oc as well.

anyways, good luck, you seem to have a fairly good chip, I would consider investing in watercooling if you want to get the full potential out of it

[Final8ty]

just a word of advice, don't bother running prime for more than half an hour. I say this because all prime does is torture the cpu, how many times a day do you think you'll be literally torturing your cpu with average load? Priming too long will infact cause some unnecessary damage to the cpu, unless you have some killer cooling, but I wouldn't trust a TRUE for that.

I would use OCCT and if it passes more than ten minutes, you're set (people have found that OCCT will cause errors in just a few minutes while it takes prime95 hours to do so). Just a word of advice, since I was totally into prime95 stability testing myself and now my cpu doesn't oc as well.

anyways, good luck, you seem to have a fairly good chip, I would consider investing in watercooling if you want to get the full potential out of it

OCCT3 error-ed at 8 minutes remaining on a 1 hour test Large Data Set. So a few minutes are not enough & now i set it for 2 hours.

[mattkosem]

just a word of advice, don't bother running prime for more than half an hour. I say this because all prime does is torture the cpu, how many times a day do you think you'll be literally torturing your cpu with average load? Priming too long will infact cause some unnecessary damage to the cpu, unless you have some killer cooling, but I wouldn't trust a TRUE for that.

I would use OCCT and if it passes more than ten minutes, you're set (people have found that OCCT will cause errors in just a few minutes while it takes prime95 hours to do so). Just a word of advice, since I was totally into prime95 stability testing myself and now my cpu doesn't oc as well.

anyways, good luck, you seem to have a fairly good chip, I would consider investing in watercooling if you want to get the full potential out of it

Thanks for the advice. I'm just trying to get the setup stable, and prime seems to be the best tool for the job so far. OCCT PT's linpak test doesn't seem to get results as quickly and prime has a pretty wide range of possible tests. So far I'm considering my CPU stable if it passes:

1. one hour of prime small FFTs (in place)
2. one hour of prime large FFTs with 1600mb allocated
3. one hour of prime small FFTs with 1600mb allocated

I'm not the kind of person that runs prime 24/7 and isn't content until it runs for a week without an error. I'm just trying to find a completely stable OC for this cpu that I just bought.

I'm planning to re-install the WC system when the new board arrives on Tuesday. I didn't install it initially because the GTZ that I have didn't include mounting hardware for AM2. I'm going to stick a Fuzion V1 that I picked up from another forum member on it along with the D5/DetroitAC top and TFC360 that I've already got.

--Matt

[AliG]

cool that should hold down the fort, I would probably stop a bit over 4ghz or whatever your max with 1.55v is. Hz won't deteriorate your cpu, but volts will, so try to keep the voltage to a minimum (ironic that cpus can't run without volts and yet too many kills them). Also I would seriously consider using OCCT over prime from now on, as I said, its much more efficient

[chew*]

My 2 cents on ACC.

It is not necesary with PH II, yes I know it enables a core that was disabled because it was "BAD" maybe the NB is weak on it, or maybe it doesn't scale well or maybe it runs really hot with all 4 who knows........

What ACC does is adds voltage to the chip, note the fact when enabled temps dissapear from AOD.......probably either shuts the thermal safeties off or AMD did not want you to know they were increasing voltage etc creating more heat............If it helps your PH II then maybe you need to fine tune your voltages a tad more ;)

The only way ACC did anything for me was on a bios that though my chip was a PH I etc, did not support PH II. It clocked higher but at the cost of performance with a bios not supporting the chip.....

[Oj101]

just a word of advice, don't bother running prime for more than half an hour. I say this because all prime does is torture the cpu, how many times a day do you think you'll be literally torturing your cpu with average load? Priming too long will infact cause some unnecessary damage to the cpu, unless you have some killer cooling, but I wouldn't trust a TRUE for that.

I would use OCCT and if it passes more than ten minutes, you're set (people have found that OCCT will cause errors in just a few minutes while it takes prime95 hours to do so). Just a word of advice, since I was totally into prime95 stability testing myself and now my cpu doesn't oc as well.

anyways, good luck, you seem to have a fairly good chip, I would consider investing in watercooling if you want to get the full potential out of it

I can run OCCT for an hour without a hitch but can't run F@H for three days. I think the ultimate stability test is the one that literally takes the longest - normal daily use :)

[AliG]

I can run OCCT for an hour without a hitch but can't run F@H for three days. I think the ultimate stability test is the one that literally takes the longest - normal daily use :)

folding is a different story. That probably is the hardest legit task since it goes on non-stop doing as many calculations as the cpu can handle (not even gaming will be close to the stress). However, for a person that does not fold, anything that lasts an hour in a stability test is more than enough

[mattkosem]

My 2 cents on ACC.

It is not necesary with PH II, yes I know it enables a core that was disabled because it was "BAD" maybe the NB is weak on it, or maybe it doesn't scale well or maybe it runs really hot with all 4 who knows........

What ACC does is adds voltage to the chip, note the fact when enabled temps dissapear from AOD.......probably either shuts the thermal safeties off or AMD did not want you to know they were increasing voltage etc creating more heat............If it helps your PH II then maybe you need to fine tune your voltages a tad more ;)

The only way ACC did anything for me was on a bios that though my chip was a PH I etc, did not support PH II. It clocked higher but at the cost of performance with a bios not supporting the chip.....

I still see temps in AOD and and CoreTemp with it enabled. I'm not sure why everyone else doesn't...

I'm running the latest bios for the board, version 802 - released in January. The release notes for it state "01. Support ACC for AM2+ 45nm CPU". Could something have been done in that bios that makes it more usable? I cannot report anything other than what I've seen on my PC. I have nothing to gain or lose by reporting my findings. I'm just reporting what I'm seeing. As I've mentioned, setting 3.7Ghz on core 3 or all 4 cores in AOD previously resulted in an almost instant reboot when under no load. This occurs at 1.40v or 1.55v and with any other variations of NB, HT, and memory voltages and timings. With ACC enabled, this does not happen and it is 3.7 is completely stable. I'm not sure why this is so difficult to believe, but I encourage others that have a weak core or weak cores on their cpu to try it. There's nothing to lose, and it provided sizable gains for me.

--Matt

[chew*]

I still see temps in AOD and and CoreTemp with it enabled. I'm not sure why everyone else doesn't...

I'm running the latest bios for the board, version 802 - released in January. The release notes for it state "01. Support ACC for AM2+ 45nm CPU". Could something have been done in that bios that makes it more usable? I cannot report anything other than what I've seen on my PC. I have nothing to gain or lose by reporting my findings. I'm just reporting what I'm seeing. As I've mentioned, setting 3.7Ghz on core 3 or all 4 cores in AOD previously resulted in an instant reboot. With ACC enabled, this does not happen and it is 3.7 is completely stable.

--Matt

Maybe you need to play with ram timings and northbridge VID then, that will probably yield the same results when dialed in.

[Steevo]

My 2 cents on ACC.

It is not necesary with PH II, yes I know it enables a core that was disabled because it was "BAD" maybe the NB is weak on it, or maybe it doesn't scale well or maybe it runs really hot with all 4 who knows........

What ACC does is adds voltage to the chip, note the fact when enabled temps dissapear from AOD.......probably either shuts the thermal safeties off or AMD did not want you to know they were increasing voltage etc creating more heat............If it helps your PH II then maybe you need to fine tune your voltages a tad more ;)

The only way ACC did anything for me was on a bios that though my chip was a PH I etc, did not support PH II. It clocked higher but at the cost of performance with a bios not supporting the chip.....

ACC does more than add voltage, it changes the timing of the cache, core and communications bus. The extra pins were tied to the new SB chipset. They have not released why it needs to be tied to the SB, some working close with AMD have mentioned internal cache timings as the biggest issue and those caused by a poor implementation of frequency control. However AMD is very tight lipped about the workings, and the pinout of the Phenom's.

[Jethro]

Where do you get that ACC just adds voltage? I suspect its doing something with timings and or drive strengths personally. Why would it be called advance clock calibration if it only altered volts etc.?

From a Rage 3d article:

After talking with a very smart Friend, we've come up with two possible ways in which ACC might interact with CPUs to produce the results seen since its introduction (it's a one or the other situation, albeit the second proposal would indirectly involve affecting the first aspects as well):

*

Change parameters dealing with asynchronous clock domains
within the chip/clock crossing, by increasing/reducing the number of sync clock cycles - this would correlate nicely with the increased OC’ing headroom aspect, as well as provide anecdotal evidence that indicates higher ACC values induce a slight reduction in performance in something like Prime 95, the core with the highest ACC modifier finishing last, whereas the opposite holds true for negative ACC values, in which case the core with the lowest ACC value finishes first - however, more testing is required to fully verify this.
*

Adjust skew/clock slew/ drive strength (adjusting drive strength affects clock slew anyhow) - this possibility correlates with the fact that "weak" CPUs seem to receive the most benefit, whilst good CPUs get almost none, whilst also explaining why extreme ACC values can cause boot failure, and why high positive values are recommended for high voltages (albeit it's hard to know what it is you're adding X% to)

Be aware that the above are at best slightly educated guesses ... there simply isn't enough data out there to deduce exactly what's going on. For all we know, miniature dwarven craftsmen could travel via the SB-CPU link to tweak the latter - at this point in time, the exact mechanism remains a mystery. However, for most people the only thing that will matter is that it pretty much works.

[mattkosem]

Maybe you need to play with ram timings and northbridge VID then, that will probably yield the same results when dialed in.

It doesn't. I've tried. It even happens with the memory set to 6-6-6-24 at 800mhz and the NB VID set to 1.40v. Believe me, I would employ some other solution if one worked. This is the only thing that has cured the issue for me. My OC on core 3 improves substantially with this change and this change only. If I had a video camera, I would record it and show you, but I don't. This brand new mobo might be faulty, and could be providing weak voltage to core 3. If that is the case, I will know on Tuesday when my new mobo arrives.

--Matt

[Jethro]

http://www.rage3d.com/reviews/mobo/amd790gx/index.php?p=3

[G0ldBr1ck]

Where do you get that ACC just adds voltage? I suspect its doing something with timings and or drive strengths personally. Why would it be called advance clock calibration if it only altered volts etc.?

From a Rage 3d article:

After talking with a very smart Friend, we've come up with two possible ways in which ACC might interact with CPUs to produce the results seen since its introduction (it's a one or the other situation, albeit the second proposal would indirectly involve affecting the first aspects as well):

*

Change parameters dealing with asynchronous clock domains
within the chip/clock crossing, by increasing/reducing the number of sync clock cycles - this would correlate nicely with the increased OC’ing headroom aspect, as well as provide anecdotal evidence that indicates higher ACC values induce a slight reduction in performance in something like Prime 95, the core with the highest ACC modifier finishing last, whereas the opposite holds true for negative ACC values, in which case the core with the lowest ACC value finishes first - however, more testing is required to fully verify this.
*

Adjust skew/clock slew/ drive strength (adjusting drive strength affects clock slew anyhow) - this possibility correlates with the fact that "weak" CPUs seem to receive the most benefit, whilst good CPUs get almost none, whilst also explaining why extreme ACC values can cause boot failure, and why high positive values are recommended for high voltages (albeit it's hard to know what it is you're adding X% to)

Be aware that the above are at best slightly educated guesses ... there simply isn't enough data out there to deduce exactly what's going on. For all we know, miniature dwarven craftsmen could travel via the SB-CPU link to tweak the latter - at this point in time, the exact mechanism remains a mystery. However, for most people the only thing that will matter is that it pretty much works.

He didnt mean that voltage is all it dose. Just that thats all that Phenom II benefits from. All the other functions of ACC were designed for Phenom I, Phenom II does not benefit from the Clock Calibration.

[Jethro]

Some Phenom II triple core's gaining a core with ACC on auto might just be considered an benifit i think :) Is it possible that this feature could come into play at some point even if it isnt a factor now? Its obviously helping Matt!!

Anything from AMD stating that it will NOT effect Phenom II's?

[chew*]

To each his own I call it placebo effect.......Your sources are people taking educated guesses.

My sources are a little more direct than that and I quote " ACC offers no benefit whatsoever with Phenom II "

It is not designed for phenom II it is not made to work with phenom II etc etc, so the only thing that it is applying is voltage......

NB is directly tied to the MMC I have tested this, at X NB vid volts my memory would not pass memtest, In test B with more than X NB vid volts it passed fine and was cinebench stable.......

It's possible that the mobo manufactureres are trying to code it in however and you guys are seeing a fluke......however Phenom II does not support it.

1.40 NB vid volts is not trying it.........taking a cpu to the max voltage the board allows is trying it....

I would love to see direct comparison benches of performance at same clocks with it off and on.

I have tested with it on BTW and although the thermal monitor went blank my K probe does not lie, a +2C jump on the edge of the IHS.

since when did gaining a bum core become benefit? If cpu with only 3 cores can do 4.3 gig and the same cpu with 4 cores can only do 3.3 gig its not much of a benefit. same scenario if cpu can do 2800-3000 NB and can only do 2400 with the 4th core enabled, wheres the benefit.

[Jethro]

Whether one percieves it as a benefit or not ACC is certainly having an effect on Phenom II's.

[chew*]

Whether one percieves it as a benefit or not ACC is certainly having an effect on Phenom II's.

Well unless we see comparison tests with and without thats sort of an open mouth statement.

I can clock higher......so its a benefit....hell I can clock 1 core higher than the others..........won't do me much good performance wise in Wprime though... see my point....

Bench comparisons at same speed enabled and disabled will determine if its truly a benefit.

Yes its definitely having an effect, lol free cores for everyone....

[Jethro]

As im reading some folks are having very positive results enabling cores on there phenom II's. Why are you so cynical>? Its all in good fun. Just chattin about it a bit man lighten up.

[Rolle2k]

Even though i also have read that ACC won't work on Phenom II i now probably have to try it, maybe tomorrow.. i have also trouble with one core.. i just have to test a little more, and if it doesnt help then i have to try this way.

[mattkosem]

Well unless we see comparison tests with and without thats sort of an open mouth statement.

I can clock higher......so its a benefit....hell I can clock 1 core higher than the others..........won't do me much good performance wise in Wprime though... see my point....

Bench comparisons at same speed enabled and disabled will determine if its truly a benefit.

Yes its definitely having an effect, lol free cores for everyone....

Well, if you can come up with a reasonable, clear, and concise plan that you would like me to execute, I'd be happy to run it. I'm only running ACC on one core. Enabling it across all cores kills the OC on cores that are otherwise working fine. I can run side by side single threaded tests chosen by you on the core with ACC and on one without. Make me a list, and I'll run through it. As you can see in the prime screenshot that I posted, all 4 cores were at the same exact point in the test after over 15 minutes and they all reached that step at the same time. I have nothing to prove, but will humor your curiosity if that's what you crave.

--Matt

[mattkosem]

Here's a quick super pi 1M test. The one on the left is from core 3 and the one on the right is from core 1. The tests were run one right after the other. They're well within a reasonable distance of eachother. The core with ACC even took a small, but negligible lead.

--Matt

[mattkosem]

And here's 32M. Only a .07% difference.

--Matt

[chew*]

PI is to inconsistent, my second PI run is almost always faster than my first.

You would need to bench maybe 3d, and multicored....cinebench gives preety consistent results when run repeatedly and is highly cpu bound.

Try running that with ACC off an on 3 times each and we will average results.

Not trying to be cynical just posting the facts that have been relayed to me.

[mattkosem]

PI is to inconsistent, my second PI run is almost always faster than my first.

You would need to bench maybe 3d, and multicored....cinebench gives preety consistent results when run repeatedly and is highly cpu bound.

Try running that with ACC off an on 3 times each and we will average results.

Not trying to be cynical just posting the facts that have been relayed to me.

Your second pi 32M run is consistently faster than the first by a consequential amount? On 1M I can understand that, but 32M runs over a long enough period of time that things like that are avoided. I've seen variations of as much as .08s between pi 1m runs on faster intel cpus, but never variations of that magnitude on 32M runs.

As I stated, I can only run single threaded tests for you to test this. ACC is only enabled on one core, and enabling it on the others at the same level causes the other cores to be unable to clock as well. If you want to see cinebench tests, I can run it once or twice with affinity set to the core with ACC and a again on a core without.

That stated, I'm still sticking with pi32M being a consistent enough bench to show these results. If you didn't miss the 32M benches that I posted and would still like to see cinebench on a single core, please specify the version that you would like to have run and I can run it.

--Matt

[chew*]

matt just run cinebench, render all cpu's with acc on that one core, then run it without acc on, if it won't pass at that speed just drop the clock down for both comparisons.

I'd like to see this because I think the difference will be most noticeable when all the cores are synced together so to speak, etc with acc on I do not think they will work in harmony as well.....

PI no matter what it is is way to inconsistent, I get diff times every single time I run it, cinebench however scores identical repeatedly and is influenced by cpu speed only, ram clocks etc do not benefit it.....

[mattkosem]

Ok. I'll have to run it at 3.5Ghz then. I'll kick Cinebench R10 off with both configurations when I get home.

--Matt

[mattkosem]

Here you go. 14767 with ACC enabled at +2% on one core, 14467 with it disabled completely.

--Matt

[chew*]

very interesting, thx matt.

[Rolle2k]

Funny thing.. my "bad" core always hanged the computer at around 3,54GHz, or prime died under running so i had to restart it.. and now i have enabled acc +2% on that core.. haven't run more than 1h 30min at same voltage, but so far it seems stable. Normally it would have errored already.. i'll post later when i have primed for longer time!

[gOtVoltage]

Funny thing.. my "bad" core always hanged the computer at around 3,54GHz, or prime died under running so i had to restart it.. and now i have enabled acc +2% on that core.. haven't run more than 1h 30min at same voltage, but so far it seems stable. Normally it would have errored already.. i'll post later when i have primed for longer time!


I knew ACC was good for more than a High oc.

If anything it brings stability for CPU's that seem to have uneven power distribution on all 4cores. Thus allowing you to tweak the Volts to compensate for stability.

Even ACC dosnt allow me Higher Overclocks vs Not using it on same Mobo . But it does Come in handy for supplying cleaner power across all 4cores when tweaked right.

[mattkosem]

Just wanted to report back. I'm running the M4A79 Deluxe now. I don't instantly reboot at 3.7 without ACC anymore, but I think that's due to the flat 12C drop in temps that the water cooling provided. Prime blend reboots the machine within 2 iterations at those settings. Setting the +2 on the problematic core has, once again, corrected that issue. Blend running 1024k FFTs pushes me to a max of 40C at 3.7Ghz with the NB at 2400. I'll see what I can do about pushing those numbers up further when I have some more time.

--Matt

[Lastviking]

With my Phenom II 940BE and Dfi 790FXB i first need to press reset after enabled acc and then it works to boot in to windows but i lose some stabilty with (acc enabled) becuse i geting blue screen next time i restart windows.

Maybe its the board or the cpu.

[ecat]

ACC does appear to gain me a little extra stability but in tests so far it has not proved worthwhile. eg.

Up the speed on my 3rd core, from observation this is the weakest, until Prime95 fails. The fail is usually a re-boot at this point. Enable ACC -2. Prime95 still fails but on a rounding error, no reboot. ACC = -4 gives the same result, ACC = -6 and it's back to reboot. Hum, it is doing something, intentional or otherwise.

[mattkosem]

ACC does appear to gain me a little extra stability but in tests so far it has not proved worthwhile. eg.

Up the speed on my 3rd core, from observation this is the weakest, until Prime95 fails. The fail is usually a re-boot at this point. Enable ACC -2. Prime95 still fails but on a rounding error, no reboot. ACC = -4 gives the same result, ACC = -6 and it's back to reboot. Hum, it is doing something, intentional or otherwise.

I'm using +2% on my weak core. -2% seems to make my results worse.

With my Phenom II 940BE and Dfi 790FXB i first need to press reset after enabled acc and then it works to boot in to windows but i lose some stabilty with (acc enabled) becuse i geting blue screen next time i restart windows.

Maybe its the board or the cpu.

Since you didn't mention having one bad core, and didn't mention enabling ACC on it and it alone, it sounds like you're going about trying ACC with the wrong approach. Have you tried OCing core by core, and run into one core that clocks worse than the others?

--Matt

[Lastviking]

I'm using +2% on my weak core. -2% seems to make my results worse.



Since you didn't mention having one bad core, and didn't mention enabling ACC on it and it alone, it sounds like you're going about trying ACC with the wrong approach. Have you tried OCing core by core, and run into one core that clocks worse than the others?

--Matt

I can do super pi1m with 1.47v(True Black air temp 25c)

Core0=4040mhz
Core1=4060mhz
Core2=4040mhz
Core3=~3950mhz

OCCT no problem @ 3.8ghz on the good ones

Have problem with Core2/Core3 changing place sometimes when i´m restarting windows(dunno know why)

ACC setting i have tryied(have done more tests before also)

ACC Enabled(Per core)

Core0=-+0
Core1=-+0
Core2=+2(have also tryied 0 here)
Core3=+2

OCCT still crash @ 3.8ghz

And super pi1m cant run @4.0ghz @ core3

[mattkosem]

I can do super pi1m with 1.47v(True Black air temp 25c)

Core0=4040mhz
Core1=4060mhz
Core2=4040mhz
Core3=~3950mhz

OCCT no problem @ 3.8ghz on the good ones

Have problem with Core2/Core3 changing place sometimes when i´m restarting windows(dunno know why)

ACC setting i have tryied(have done more tests before also)

ACC Enabled(Per core)

Core0=-+0
Core1=-+0
Core2=+2(have also tryied 0 here)
Core3=+2

OCCT still crash @ 3.8ghz

And super pi1m cant run @4.0ghz @ core3

Bummer. I haven't had any luck with values over 2, but you could give 4 a shot. *shrug*

--Matt

[chris.y2k.r1]

folding is a different story. That probably is the hardest legit task since it goes on non-stop doing as many calculations as the cpu can handle (not even gaming will be close to the stress). However, for a person that does not fold, anything that lasts an hour in a stability test is more than enough

I could not disagree more - For as long as you run OCCT it can fail. I've seen it fail @ 1 minute, 1 second, 1 hour, 1 day, 5 hours ....on and on... When your system is right it will run anything forever - when it's not it won't period. If you think OCCT 1 hour is good enough that you are going to crash at some point whether it's gaming or whatever. Unless you got really lucky with your settings, 24/7 stability cannot be assumed at all after 1 hour of OCCT. Maybe after 30 hours you might be alright. I use tests of all sorts. Sometimes OCCT will runs for hours and SPI 32M will crap out at iteration 4.

[chris.y2k.r1]

I have a question - If ACC does nothing for Phenom IIs then why is it installed in AM3 boards? AMD is being tight lipped about this for a reason. I suspect it's something like the TLB issue.

[chew*]

I have a question - If ACC does nothing for Phenom IIs then why is it installed in AM3 boards? They can't run Phenom I's anyway - So that's just straight BS. AMD is being tight lipped about this for a reason. I suspect it's something like the TLB issue.

Future proofing? Sort of like sideport on ati cards...its there but it doesn't work. No clue really.

[mattkosem]

Future proofing? Sort of like sideport on ati cards...its there but it doesn't work. No clue really.

As I've been saying, it definitely works. It may not be as drastic of an improvement as it was on PHI, but it does make an improvement. It also seems to need additional increases as the clock and/or voltage is increased. I had to bump it up to 2%/2%/4%/4% at 1.6125v for 3.82Ghz on my M4A79 Deluxe. I require 4%/4%/4%/4% at 1.6375 to bench at 3.92Ghz. Asus actually fixed it in the 1102 bios for this board. It was very apparent that it wasn't working in the 90x and 100x bios builds.

--Matt

[chew*]

As I've been saying, it definitely works. It also seems to need additional increases as the clock and/or voltage is increased. I had to bump it up to 2%/2%/4%/4% at 1.6125v for 3.82Ghz on my M4A79 Deluxe. I require 4%/4%/4%/4% at 1.6375 to bench at 3.92Ghz.

--Matt

Yes i know it works in your case for AM2+ matt, its also included in am3 board bios's and the for the record chat is " it does nothing for am3 " but it's still being coded into the bios. Its apparently doing something though as it is enabling dead cores on AM3.

Your chip seems to be an anomally, like one rare case of it making a diff.....and actually getting measurable performance increases when enabled.....its possible your chip made it through binning that it shouldn't have somehow with a weak core.

[Smartidiot89]

Yes i know it works in your case for AM2+ matt, its also included in am3 board bios's and the for the record chat is " it does nothing for am3 " but it's still being coded into the bios. Its apparently doing something though as it is enabling dead cores on AM3.

Your chip seems to be an anomally, like one rare case of it making a diff.....and actually getting measurable performance increases when enabled.....its possible your chip made it through binning that it shouldn't have somehow with a weak core.
Have AMD actually said that ACC doesn't work with Phenom II?

It's not impossible it does actually help, I have yet to see extensive testing proving the opposite, or a database of people saying it didn't work.

And why wouldn't hes chip make it through the binning? It is stable at stock, I don't think AMD cares if the chip can overclock to 3,5ghz or 3,7ghz as long as stock values (and lil bit above) is working fine.

[chew*]

Have AMD actually said that ACC doesn't work with Phenom II?

It's not impossible it does actually help, I have yet to see extensive testing proving the opposite, or a database of people saying it didn't work.

And why wouldn't hes chip make it through the binning? It is stable at stock, I don't think AMD cares if the chip can overclock to 3,5ghz or 3,7ghz as long as stock values (and lil bit above) is working fine.

Yes they have thats why I have said what i said....I say made it through binning becasue without acc on his performance is somewhat hindered.

[keithlm]

Have AMD actually said that ACC doesn't work with Phenom II?


As far as I know: The ONLY source on this was a third party reviewer at a website that claimed that ACC was built into the PHII chips and it was not needed or used. He claimed that his source at AMD confirmed that.

BUT when you have a few bios updates that specifically mention fixing ACC for PHII chips that kind of contradicts the reviewer. Plus not having any concrete information from AMD doesn't help.

Perhaps the reviewer's "source" at AMD meant that it wouldn't work with the bios that was then available and he interpreted that in his own way. (And of course the way the internet works... pretty soon other sources were quoting him.)

[mattkosem]

This guy seems to be having pretty good luck with ACC on his PHII as well: http://forums.ncix.com/forums/?mode=showthread&forum=195&threadid=1958407&pagenumber=1&msgcount=15&subpage=1

--Matt

[chew*]

This guy seems to be having pretty good luck with ACC on his PHII as well: http://forums.ncix.com/forums/?mode=showthread&forum=195&threadid=1958407&pagenumber=1&msgcount=15&subpage=1

--Matt

Matt your missing the big picture. 2 people so far with good accounts.......out of how many? I still say anomally.

My sources are not stuff you guys read on the net ;)

[mattkosem]

Matt your missing the big picture. 2 people so far with good accounts.......out of how many? I still say anomally.

My sources are not stuff you guys read on the net ;)

I don't think the big picture is worth that much in this case. Your sources must not be folks at AMD or at any of the mobo manufacturers that have added improvements for ACC in recent bios builds. I'm sure they wouldn't bother with making these improvements if they were all for naught. If it works for two it can work for others. The "ACC Doesn't Do Anything on Phenom II" attitude is preventing people from giving it a shot in the first place.

--Matt

Edit: here's my latest achievement, thanks to a bit more voltage and some additional ACC tweaking.

[soundood]

I don't think the big picture is worth that much in this case. Your sources must not be folks at AMD or at any of the mobo manufacturers that have added improvements for ACC in recent bios builds. I'm sure they wouldn't bother with making these improvements if they were all for naught. If it works for two it can work for others. The "ACC Doesn't Do Anything on Phenom II" attitude is preventing people from giving it a shot in the first place.

--Matt

Edit: here's my latest achievement, thanks to a bit more voltage and some additional ACC tweaking.

why does the AM3 boards have ACC in the SB750 SB?

[mattkosem]

why does the AM3 boards have ACC in the SB750 SB?

It doesn't seem to be known at the moment. There are reports that it isn't needed for AM3, but there are also similar reports about the AM2+ Phenom IIs. I'll certainly give it a try when the 955 comes out though!

--Matt

[chew*]

Matt my source is AMD, I don't know what else to tell you.....it seems to work on a couple chips.....buy 4 more 940's and do a comparison....best I can tell you.

[G0ldBr1ck]

I would guess that in some cases where ACC creates more stability its due to a shortcoming of the MB. When ACC is enabled from what I understand, the clock is generated off of a diffrent PLL and accesses the die by a different circuit. If the boards default clockgen and circuits are not up to 100% perfect in function and the ACC southbridge clockgen is, it could make a large impact on stability.

I would also speculate that its threw this other link from the southbridge that is accessing the fused off cores and cache that aparently were only fused off from the default link.

This of course is all just speculation.

[mattkosem]

Matt my source is AMD, I don't know what else to tell you.....it seems to work on a couple chips.....buy 4 more 940's and do a comparison....best I can tell you.

I surely won't buy any more 940s with 955 right around the corner. My 940 does 3.82Ghz 24/7 stable with the help of ACC. Aside from having you test this processor yourself, there's nothing else that I can really do to prove this to you (if you really want to see it, I'd entertain an X3 920BE to x4 940BE swap). Trust me though, it does actually help in some cases. It helped on two different boards with this chip. It does seem to have one or two cores that aren't as strong as the rest but ACC definitely makes a difference, even on the stronger cores (as can be seen in the 3.825ghz shot).

--Matt

[chew*]

I surely won't buy any more 940s with 955 right around the corner. My 940 does 3.82Ghz 24/7 stable with the help of ACC. Aside from having you test this processor yourself, there's nothing else that I can really do to prove this to you. Trust me though, it does actually help in some cases. It helped on two different boards with this chip. It does seem to have one or two cores that aren't as strong as the rest but ACC definitely makes a difference, even on the stronger cores (as can be seen in the 3.825ghz shot).

--Matt


Oh i believe you matt 100% your cinebench was more than enough to convince me that its definitely helping your chip, by quite a bit I might add especially performance wise, It's just not supposed to make a diff and I have no explanation why its working for you.....I have same board, it kills all my 940's performance. I tried duplicationg results ;)

[chris.y2k.r1]

I would guess that in some cases where ACC creates more stability its due to a shortcoming of the MB. When ACC is enabled from what I understand, the clock is generated off of a diffrent PLL and accesses the die by a different circuit. If the boards default clockgen and circuits are not up to 100% perfect in function and the ACC southbridge clockgen is, it could make a large impact on stability.

I would also speculate that its threw this other link from the southbridge that is accessing the fused off cores and cache that aparently were only fused off from the default link.

This of course is all just speculation.

Sounds like it's reasonable to me. I was curious as to why there's no PLL control for AMD chips - and I like how this explanation fits the reasoning for the 4th core activation. I guess the question is how does AMD typically deactivate cores? Is it by not sending a loop?

[Smartidiot89]

As far as I know: The ONLY source on this was a third party reviewer at a website that claimed that ACC was built into the PHII chips and it was not needed or used. He claimed that his source at AMD confirmed that.

BUT when you have a few bios updates that specifically mention fixing ACC for PHII chips that kind of contradicts the reviewer. Plus not having any concrete information from AMD doesn't help.

Perhaps the reviewer's "source" at AMD meant that it wouldn't work with the bios that was then available and he interpreted that in his own way. (And of course the way the internet works... pretty soon other sources were quoting him.)
Yepp, so unless I see a statement and a source directly from AMD I won't believe otherwise.

ACC might not help as much as it did to Agena (K10 65nm), but it could be working to some extent.

The fact that many motherboard manufacturers just "fixed ACC" many have already forgotten about this function and have not bothered to try it with new BIOSes and to fully take advantage of ACC actually requires loads of patience, as in trying to find out which core is weak, before using this function.

I am not calling you a liar Chew* but unless you can show me a concrete source from AMD, I won't be the one saying that Phenom II isn't supported by ACC "unless a defect passed through binning" which isn't a viable theory at all to me.

[chew*]

Yepp, so unless I see a statement and a source directly from AMD I won't believe otherwise.

ACC might not help as much as it did to Agena (K10 65nm), but it could be working to some extent.

The fact that many motherboard manufacturers just "fixed ACC" many have already forgotten about this function and have not bothered to try it with new BIOSes and to fully take advantage of ACC actually requires loads of patience, as in trying to find out which core is weak, before using this function.

I am not calling you a liar Chew* but unless you can show me a concrete source from AMD, I won't be the one saying that Phenom II isn't supported by ACC "unless a defect passed through binning" which isn't a viable theory at all to me.

The defect is my analogy for it as there is no logical explanation for it.....call it a hypothesis if you will.........

As far as my source.....laughable?

You seriously can't just expect me to drop a name or drag someone in here........take or leave it for what its worth....but ACC is not designed for PH II and PH II is not designed to work with ACC........whatever the bios guys and motherboard manufacturers are doing I have no clue.....makes little sense to me.....I can see patches for existing support for am2+ boards making sense........the AM3 boards are making no sense......I believe most of the patches are killing the ability to use the extra core though so that should tell you something in itself.

Btw yes ACC enables a core on my asus with a specific bios, disable ACC and the chip runs smooth as butter and is very responsive......enable it and I have to fight with the board the entire time to do what I want to do.......ya ya its a bad core.....does more than my 940 so it's not that bad ......it at least boots over 1.6v on air.

[Smartidiot89]

The defect is my analogy for it as there is no logical explanation for it.....call it a hypothesis if you will.........

As far as my source.....laughable?

You seriously can't just expect me to drop a name or drag someone in here........take or leave it for what its worth....but ACC is not designed for PH II and PH II is not designed to work with ACC........whatever the bios guys and motherboard manufacturers are doing I have no clue.....makes little sense to me.....I can see patches for existing support for am2+ boards making sense........the AM3 boards are making no sense......I believe most of the patches are killing the ability to use the extra core though so that should tell you something in itself.

Btw yes ACC enables a core on my asus with a specific bios, disable ACC and the chip runs smooth as butter and is very responsive......enable it and I have to fight with the board the entire time to do what I want to do.......ya ya its a bad core.....does more than my 940 so it's not that bad ......it at least boots over 1.6v on air.
No I don't expect you to drop a name, but unless AMD gives out info in public clearly stating ACC isn't working :shrug: A link from a trustworthy website with a "anonymous" source from AMD would be enough for me.

Also that the new BIOSes doesn't allow people to activate the 4th Core, is because AMD kindly requested all motherboard manufacturers to make this change to ACC, cause they didn't like the idea of people buying X3's and unlocking them, I thaught everyone knew about this? So no it doesn't tell me something in itself.

And you said it yourself you have no idea what the AM3 manufacturers are doing implementing ACC.

And as we can see ACC is working for this guy, he does gain stability from it, hes clock was unstable until he used ACC.

[chew*]

No I don't expect you to drop a name, but unless AMD gives out info in public clearly stating ACC isn't working :shrug: A link from a trustworthy website with a "anonymous" source from AMD would be enough for me.

Also that the new BIOSes doesn't allow people to activate the 4th Core, is because AMD kindly requested all motherboard manufacturers to make this change to ACC, cause they didn't like the idea of people buying X3's and unlocking them, I thaught everyone knew about this? So no it doesn't tell me something in itself.

And you said it yourself you have no idea what the AM3 manufacturers are doing implementing ACC.

And as we can see ACC is working for this guy, he does gain stability from it, hes clock was unstable until he used ACC.

OK it works for 2 people that we have accounts of.... does acc do anything for you? try it ;)

[Smartidiot89]

OK it works for 2 people that we have accounts of.... does acc do anything for you? try it ;)
ACC is still a marketing thing, and you seriously think everyone reports it when it works, and you think that every single overclocker in the entire world sits here on XS?

Seriously an "anomaly" that makes ACC work for Phenom II doesn't make any sense whatsoever.

Show me something to prove me wrong and I will shut my mouth promise.

[chew*]

I'm not the one that has to prove anything, your backing up other reports that it helps with no supporting results of your own.......

to conduct or start a theory you need to test a large group of cpu's I would be interested to hear matts take on this once again when he gets a AM3 chip.

I have tested with lets see.......I have 9 PH II chips here and out of 9 chips it made 9 chips less stable on 3 diff motherboards........and unlocked two.

Don't know what else to say......I have tried and have not been able to duplicate it.

Matts results are indeed interesting, but with what I have here I still have yet to duplicate it, I have the same board and bios so thats not the issue........

Remember there are always the anomalies or chips that break the rules just like with the batch theories........theres always a few that are an exception to the rule......I have one chip that refuses to post at 1.6vcore on air no matter how cold the air is (0C ambients) all my other chips can boot fine above 1.7v.............but get it colder and its fine and acts like the other chips

[Smartidiot89]

Phenom II is nothing but a remake of Phenom, wich ACC officially was implemented on. It's not entirely impossible some remnants of the ACC functions caried over to Phenom II, and I think Matts proved that in some cases, ACC makes a difference.

And yes I will try it on my motherboard when I have the time, but I won't say ACC is useless because I myself can duplicate what someone else has accomplished.

[chew*]

Phenom II is nothing but a remake of Phenom, wich ACC officially was implemented on. It's not entirely impossible some remnants of the ACC functions caried over to Phenom II, and I think Matts proved that in some cases, ACC makes a difference.

And yes I will try it on my motherboard when I have the time, but I won't say ACC is useless because I myself can duplicate what someone else has accomplished.

Sorry wasn't aware you were in on the design team of phemon II to make that claim.....my source however was.....Not going to argue this though as this is pointless and i'm beating a dead horse......this is why I dont bother sharing information.....

[Smartidiot89]

Sorry wasn't aware you were in on the design team of phemon II to make that claim.....my source however was.....Not going to argue this though as this is pointless and i'm beating a dead horse......this is why I dont bother sharing information.....
No I am not, but ACC has worked for Phenom II so what are you going on about, I am just coming up with a theory as to why thats all and sources claim that Phenom II is based upon Phenom so it makes total sense to me why it works in rare cases :confused:

Also ACC doesn't only change voltage, it does lots of things to the CPU, like others has mentioned in this thread

[chew*]

No I am not, but ACC has worked for Phenom II so what are you going on about, I am just coming up with a theory as to why thats all and sources claim that Phenom II is based upon Phenom so it makes total sense to me why it works in rare cases :confused:

Also ACC doesn't only change voltage, it does lots of things to the CPU, like others has mentioned in this thread

Phenom II is a totally diff animal.......if not it would have the same cold bug.....IIRC ACC's original purpose was to attain higher clocks on PH 1 not make clocks stable....so far no one is getting "Higher clocks" they are just getting stable which brings me back to the point that those finding it to work are just missing certain settings or not setting them "just right"

[mattkosem]

so far no one is getting "Higher clocks" they are just getting stable which brings me back to the point that those finding it to work are just missing certain settings or not setting them "just right"

I'm a little thrown off by this chew. It's not a fine tuning issue that is corrected by ACC on this chip. As I mentioned, the system instantly reboots at higher clocks without it. I am definitely getting higher clocks with it enabled.

Example: 3.8Ghz

I cannot boot into windows at this clock without ACC enabled on at least the last two cores. It BSODs on startup. If I set the clock to 3.8 in Windows with ACC disabled, it reboots instantly. +2% on the last cores allows me to get into windows at that clock, but it fails prime, spi, etc. +%2 on the first two and +4% on the last two brings me stable at 3.8.

--Matt

[demonkevy666]

ACC is a PLL used in the south bridge because the original phenom PLL didn't work properly on die. When ACC is enforced is uses this PLL off the chip to control the clock better a side effect is it can rise volts of the chip on load. CPU vdda is the PLL voltage.
phenom II is design with straining and immersion lithography it's more accurately designed now

[Lastviking]

Phenom II 940BE and Dfi 790FXB tested all ACC setting... +12 to -12(All cores and per core)... Most stabilty is ACC Disabled for me +- ACC = Blue screen more early.

[G0ldBr1ck]

A new thread for testing and results like /\ could be quite informative if others would be willing to test it also.

[shaolin95]

In any case I take it that any + means higher OC chance and any -% means a more agressive setting right?

[chew*]

In any case I take it that any + means higher OC chance and any -% means a more agressive setting right?

No it was/is chips dependant.