Phenom II ddr III speed vs timings

[roofsniper]

yes ddr3 has brought on a new wave of confusion. ddr2 was pretty straight forward and you would go for the highest clocks you could get now its just like wtf guess check and revise? well my other calculation was around 3.2ghz nb which would make sense and also agree with demonkevy's though too. but wouldnt 1800 7-7-7 always be faster than 1700 9-9-9 because the timings are lower and the clocks are higher? if you got anything else to show that would be nice. it might take time to get used to this whole ddr3 thing. but hows it on intel's side? did they ever have similar issues on core 2 or i7 with ddr3? seems kinda pointless to be making ram that can run at speeds like 2200 mhz if speeds much lower seem to perform better.

[chew*]

yes 1800 7-7-7 should be always faster than 1700 9-9-9 but it was not faster by a large margin as was previously seen with ddr 2.......

.05 in PI 1m is small potatoes considering those timings and speeds. In real world we are talking about 1/10th of a FPS better in a game? not worth the effort or money

[roofsniper]

well how can you explain this? the ram is too fast for the imc? the ram is too fast for the cpu itself? how can this be fixed? because really i see no point in ddr4 if they cant find a way within the next few years to take advantage of all the bandwidth. unless they make a gpgpu.

[chew*]

well how can you explain this? the ram is too fast for the imc? the ram is too fast for the cpu itself? how can this be fixed? because really i see no point in ddr4 if they cant find a way within the next few years to take advantage of all the bandwidth. unless they make a gpgpu.

they have either eliminated a bottleneck and or created another bottleneck........maybe something we won't be able to get around until we get a new NB or SB?

The other possibility is they tuned it that way for a reason.......so that air/water users would get the max performance without killing themselves to get high clocking ram stable.........It not like the platform is bandwidth starved atm anyway..........

[crazydiamond]

maybe something we won't be able to get around until we get a new NB or SB?

this is what i was thinking between imc revisions and the new chipset coming out hopefully we can start to see some nb clocks that make the ram shine

[Oese]

ok did some testing with latency dependant super pi 1m (1600 mode vs. 1333 mode) to see if there's really a slowdown with 1600 mode:



to compare, i'll calculate the average of each of those two runs:

run 1 (1333 mode): 18.545s
run 2 (1600 mode): 18.565s
run 3 (1600mode slow nb): 18.617s
run 4 (1333mode slow nb): 18.626s

i think not much difference at all. variability in those runs is higher then difference in mean values. differences are most likely found to be due to nb speed... ~50ms count for 200mhz nb, so 10ms can easily be due to 50mhz more or less nb speed when comparing run 1 to run 2... thus no problem with running 1600 divider i think..

next up i'll do vantage and 3dm06 to compare 1333 cl6 with 1600 cl7 as a more bandwidth-dependent bench...

[Zeus]

1M is not memory intensive as the large cache of the cpu is mainly used for 1M calculation instead of the ram, hence the faster 1M calculation time when raising NB-CPU frequency. (=faster acces to the cpu cache)

If you want to test memory performance 32M is best but it will take ages to test.

[Oese]

agree, thats why there's no difference between 1333 cl6 and 1600 cl7. bandwidth does not count here. latency is a factor though. one can prove that by comparing ddr3-1333 cl7 to ddr3-1333 cl6.



thus, slower overall latency settings in the imc when 1600 mode is chosen should have an effect when doing a latency-dependent bench. Thats what i tested, and i didnt find such....

here you can see the effect of latency/bandwidth as well:



1333: 6-5-5-18: 3dm06 21265, cpu 5510, sm2 8480, sm3 10337; vantage 13742, cpu 13654, graphics 13771
1333: 6-6-6-18: 3dm06 21217, cpu 5548, sm2 8378, sm3 10346; vantage 13703, cpu 13715, graphics 13700
1600: 7-6-6-20: 3dm06 21285, cpu 5514, sm2 8481, sm3 10355; vantage 13620, cpu 13690, graphics 13596
1600: 7-7-7-20: 3dm06 21236, cpu 5482, sm2 8441, sm3 10372; vantage 13722, cpu 13638, graphics 13750

mmh not really consistent findings here... seems all is within range of variability..

[bro20000]

Have found that 1700Mhz 6-6-6-15-18 is the fastest for me without a doubt! Bit of both high bandwidth and low latency!

[Oese]

haha lucky one

[bro20000]

Sorry about that it meat to say 1600Mhz 6-6-6-15-18
Need 2.0v for 1700Mhz 6-6-6-15-18 and am not happy using that voltage 24/7! Prefer using 1.65v for 1600Mhz 6-6-6-15-18

[Oese]

hehe sure

[massman]

Oh, good thread. I already had some thoughts regarding the need for high frequency DDR3 memory when comparing the AM3 with AM2+ motherboards.

http://www.madshrimps.be/?action=get...58&articID=926

Check out the Lavalys Everest results in the overclocked test setting: 750MHz 7-6-6-18 performs pretty much the same as 600MHz 4-5-5-16 :-)