680i ram timing guide

[illuminati-hwt]

Hi mates,

I made a ram timing guide kinda like the "old DFI-street guide".
The guide can be found at evga's forum, fell free to check it and comment.
http://www.evga.com/community/messag...TOPIC_ID=32135

I also made a Bios flash guide with bios collection, FAQ and OC-guide:
http://www.evga.com/community/messag...TOPIC_ID=30071


edit: copy/pasted the thread and redid the formatting


Ram timing guide

As you can imagine, this has taken a lot of testing. 40-something benchmarks actually [] On to the point..

Each chipset (680i/975/965) acts differently to how timings are applied.
Some of you are probably familiar with how DDR1 ram acted on timings - DDR2 acts a bit differently and some timings are less important than what they used to be.

The EVGA 680i SLI board has an entire bios section dedicated to ram timings. So why not do some tweaking.
The guide follows the bios order, skipping Command Per Clock which is saved for last.

The section looks like this:



I've tested all timings one by one. Sisoft Sandra 2007 was used for benchmarking. All the first benchmark results were discarded since they tend to fluctuate.

My ram specs:
2x1gb Corsair PC2-8500C5 (D9)
Unlinked to 800mhz @ 2,175v
In blue DIMMs, running dual chan.
Base timings used: 5-4-4-12-(2T) / 3-23-5-9-(7,8)
Base Sisoft score: Int: ~5580 / Float: ~5570


tCL:
Large influence on stability / Medium influence on bandwidth
From CAS 5 to 4 results change ~5-10mb/s. The same change will most likely be seen when going to CAS 3.
This timing is widely seen as most important (Command rate disregarded).
Recommendation: 4 for normal usage, 5 when oc'ing. Tweaked: 3.


tRCD:
Medium influence on stability / Large influence on bandwidth
tRCD going from 4 to 3 gives ~15mb/s. From 5 to 4 also yields 10-15mb/s.
This timing is considered second important after CAS, but actually it's more important on 680i/DDR2.
Recommendation: 4 for oc/normal usage. 5 if you want to push mhz. Tweaked: 3


tRP:
Medium/small influence on stability / Small influence on bandwidth
Results vary close to nothing when changing from 3 to 4 to 5.
Still this timing needs to finish its cycle before a new one starts, so dont set it higher than 5.
Recommendation: 4 for oc/normal usage. 5 if you want to push mhz. Tweaked: 3


tRAS:
Small influence on stability / Small influence on bandwidth
tRAS seems to act differently on integer/float results. Integer, going from 15 to 10 changes by ~5mb/s. Float doesnt change.
tRAS is an "end-timing", so dont go to high. And not lower than what tCL+tRCD equals.
Recommendation: 12 for oc/normal usage. 15 if you want to push mhz. Tweaked: 8


tRRD:
Small influence on stability / Small influence on bandwidth
tRRD of 2 didnt change the results. Nor did a tRRD of 4. This is a delay-timing so a too low value may result in recalculation.
Recommendation: Auto for oc/normal usage. 4 if you want to push mhz. Tweaked: 2


tRC:
Medium influence on stability / Large influence on bandwidth
This timing is quite surprising. Going from 30 to 21 gave ~90mb/s. From 23 to 21 gave ~15-20mb/s.
tRC is last timing before ram burst (data transfer).
Dont set too high. And tRC should be greater than tRAS + tRP or you might get corruption.
Recommendation: 21 for normal usage. 30 if you want to push mhz. Tweaked: 15


tWR:
Small influence on stability / Small influence on bandwidth
Small change from 6 to 3. Setting timing too low will cause ram to fail switching to "read mode".
Recommendation: Auto for oc/normal usage. 6 if you want to push mhz. Tweaked: 3


tWTR:
Large influence on stability / Small influence on bandwidth
From 10 to 8 didnt change results. 6 would lock up the system. This timing gives no bonus but affects stability a lot. Use with care.
Recommendation: Auto for oc/normal usage. 10 if you want to push mhz. Tweaked: 8(7)

tREF:
Small influence on stability / Small influence on bandwidth
Changing to 3,9us didnt show improvements in benchmark. It also didnt seem to affect stability. tREF was important with DDR1.
Recommendation: Auto for oc/normal usage. 7,8us if you want to push mhz. Tweaked: 3,9us


Command Rate:
Settings are 2T/1T. You probably already know a lot about this timing.
The 680i struggles running 1T above 800mhz. So do the ram - atleast 2,2v are needed.
This timing gives a great boost to bandwidth, but is fairly hard to attain.
I wont recommend any setting regarding this timing. You need to find what mhz you get with 1T, then find mhz with 2T, then compare benchmarks.


Post words:
The tRC and tRCD are two timings to take notice of. They yield good results compared to how they affect stability.
CAS isnt as important as in the DDR1 days. You might even say timings in generel arent as important as with DDR1.

To read more on the technical aspect of DDR2 go here:
http://www.digit-life.com/articles2/...ddr2-rmma.html

If you feel like messing with timings from Windows, try this tool:
http://peecee.dk/uploads/0307/memset-3.2.zip
Note: CAS(tCL) timing cannot be changed.

Feel free to add/correct me if you have anything..

Happy tweaking! []

[goatboy]

Looks like a lot of work. Good job. Thanks!

[nugzo]

Real nice job. That should help alot of people. Thanks!

[Solarfall]

thanks for this, should prove helpful, it must have taken a lot of time to do that guide.

[illuminati-hwt]

I've added/changed my recommendation for tRC.
It seems 14/15 is a sweetspot. 13 gave lower bandwidth, but upping voltage might help.

I love the tRC timing :-)

[Yoxxy]

TRC less than CAS + TRAS == Corrupt OS.

For benching it doesn't matter but in the long run you will end up with a corrupt os.

[illuminati-hwt]

Yoxxy, as far as I remember it's actually tRC not less than tRP+tRAS. I'll check up on it.

edit. Yep.

tRC and tRAS start. tRAS ends, tRP starts. tRP and tRC end.
So tRC needs to finish at the same time or after tRP. Else the tRC will have to redo its clock-cycle.

[NinjaZX6R]

Thanks a million. As soon as a 680i board shows up at my door, this will be the first thread I turn to. Thanks for putting in the time to help others.

-Collin-

[Baleful]

Wow, thanks for the guide! I've never overclocked ram before, so when my 680i and other components get here, this will be a great deal of help! Thanks alot

[illuminati-hwt]

np mates :-)

Anyone found a sweetspot yet?

I'm at 2,1v 800mhz 4-3-4-10-2T-Auto-15-Auto...

[pumbertot]

yeah without spending much time I pretty much saw what you are saying. actually memtest is a good way to see what affects bandwidth and as you have shown many of the timings do absolutely next to nothing. i found 4-3-3 no faster than 4-4-4 in most benchmarks, only a little bandwidth. this is so different from the 965 chipset which shows a lot more variance.

[sdumper]

Great thread!

[ineedaname]

I dunno about u but my ram runs happily at 900mhz on 1t but can't even do over 1130 with 2t. Where 900mhz 1t runs faster than 1130 2t.

So i wouldn't quite say it struggles with 1t at 800.

Just trying 2 make constructive comments not trying 2 bash ur guide.

[IluvIntel]

I have a BFG 680i SLi mobo, this guide should be right for it?

[GAR]

I have a BFG 680i SLi mobo, this guide should be right for it?

Yes, same board.

[slim142]

illuminati, I followed your guide

My memory is running at 4-3-3-7 right now. I heard of people running at 4-3-3-5 but you said that tRAS should not be lower than CL and RCD (Which equal 7).

Am I good or should I try 4-3-3-5 and just leave it there?

[lopri]

I agree with most of OP's findings. Although since this is 'XtremeSystems.org', one could imagine that a little bit (1~3 ns depending on which) tighter timings are possible.

1T is undoubtedly the king of the hill with this chipset as far as performance goes. Recent BIOS seems to allow 1T a lot more easily than earlier BIOS so give it a try. I even ran 1T with all 4 slots filled and the performance is second-to-none.

However, I didn't find any significant effect of tRC on performance. Surely it affects stability if too tight, though.