Notes on performance with OCed RAM

I have seen the benefits of 1T command timing listed on various reviews around the web. I have also had people around here point out its performance advantages. I switched from DDR2-1066 @ 5-5-5-15-2T (22TRC) w/2.2v to DDR2-800 @ 4-4-4-12-1T (17TRC) w/2.2v. I saw a very small performance drop with SuperPi after that change.

I have recently picked this line of questioning up again. I found that Sandra XI has a free "lite" version and have been using that to investigate performance on my OCed system with different memory setups.

I found that my RAM was stable with settings of 916.7Mhz @ 4-4-4-12-1T (20TRC) w/2.45v, so I benched that vs my 1066.7Mhz settings (EDIT: as well as DDR2-733 @ 4-4-4-12-1T (17TRC) w/2.2v.), using the Memory Bandwidth and Memory Latency modules. I found the numbers interesting, so I decided to share. What does everyone think of these results based on these different overclocks?

916.7Mhz/1T

Memory Latency (Random Access) : 61 ns
Speed Factor : 65.9

details
1kB Range : 3.0 clk (~0.9 ns)
4kB Range : 3.0 clk (~0.9 ns)
16kB Range : 3.0 clk (~0.9 ns)
64kB Range : 14.1 clk (~4.3 ns)
256kB Range : 15.7 clk (~4.8 ns)
1MB Range : 16.1 clk (~4.9 ns)
4MB Range : 34.1 clk (~10.3 ns)
16MB Range : 53.6 ns (177.0 clk)
64MB Range : 60.6 ns (200.1 clk)​

Memory Latency (Linear Access) : 8 ns
Speed Factor : 9.2

details
1kB Range : 3.0 clk (~0.9 ns)
4kB Range : 3.0 clk (~0.9 ns)
16kB Range : 3.0 clk (~0.9 ns)
64kB Range : 12.3 clk (~3.7 ns)
256kB Range : 12.3 clk (~3.7 ns)
1MB Range : 12.4 clk (~3.7 ns)
4MB Range : 14.5 clk (~4.4 ns)
16MB Range : 8.4 ns (27.8 clk)
64MB Range : 8.4 ns (27.9 clk)​

RAM Bandwidth Int Buff'd iSSE2 : 7536 MB/s
RAM Bandwidth Float Buff'd iSSE2 : 7572 MB/s

details
Int Buff'd iSSE2 (Integer STREAM) Results Breakdown
Assignment : 7326MB/s
Scaling : 7351MB/s
Addition : 7761MB/s
Triad : 7708MB/s
Float Buff'd iSSE2 (Float STREAM) Results Breakdown
Assignment : 7376MB/s
Scaling : 7334MB/s
Addition : 7797MB/s
Triad : 7784MB/s
Warning 5010 : Cannot use Large Memory Pages due to lack of privileges.​

1066.7Mhz/2T

Memory Latency (Random Access) : 65 ns
Speed Factor : 70.5

details
1kB Range : 3.0 clk (~0.9 ns)
4kB Range : 3.0 clk (~0.9 ns)
16kB Range : 3.0 clk (~0.9 ns)
64kB Range : 14.1 clk (~4.3 ns)
256kB Range : 15.7 clk (~4.8 ns)
1MB Range : 16.1 clk (~4.9 ns)
4MB Range : 34.8 clk (~10.6 ns)
16MB Range : 57.3 ns (188.9 clk)
64MB Range : 64.6 ns (213.0 clk)​

Memory Latency (Linear Access) : 9 ns
Speed Factor : 9.5

details
1kB Range : 3.0 clk (~0.9 ns)
4kB Range : 3.0 clk (~0.9 ns)
16kB Range : 3.0 clk (~0.9 ns)
64kB Range : 12.3 clk (~3.7 ns)
256kB Range : 12.3 clk (~3.7 ns)
1MB Range : 12.4 clk (~3.7 ns)
4MB Range : 14.6 clk (~4.4 ns)
16MB Range : 8.7 ns (28.7 clk)
64MB Range : 8.7 ns (28.7 clk)​

RAM Bandwidth Int Buff'd iSSE2 : 7531 MB/s
RAM Bandwidth Float Buff'd iSSE2 : 7533 MB/s

details
Int Buff'd iSSE2 (Integer STREAM) Results Breakdown
Assignment : 7325MB/s
Scaling : 7295MB/s
Addition : 7768MB/s
Triad : 7738MB/s
Float Buff'd iSSE2 (Float STREAM) Results Breakdown
Assignment : 7316MB/s
Scaling : 7334MB/s
Addition : 7719MB/s
Triad : 7765MB/s
Warning 5010 : Cannot use Large Memory Pages due to lack of privileges.​

EDIT:

733Mhz/1T/Sync mode

Memory Latency (Random Access) : 66 ns
Speed Factor : 72.4

details
1kB Range : 3.0 clk (~0.9 ns)
4kB Range : 3.0 clk (~0.9 ns)
16kB Range : 3.0 clk (~0.9 ns)
64kB Range : 14.0 clk (~4.3 ns)
256kB Range : 15.6 clk (~4.7 ns)
1MB Range : 16.0 clk (~4.8 ns)
4MB Range : 35.1 clk (~10.6 ns)
16MB Range : 58.5 ns (193.0 clk)
64MB Range : 65.9 ns (217.4 clk)​

Memory Latency (Linear Access) : 9 ns
Speed Factor : 9.6

details
1kB Range : 3.0 clk (~0.9 ns)
4kB Range : 3.0 clk (~0.9 ns)
16kB Range : 3.0 clk (~0.9 ns)
64kB Range : 12.2 clk (~3.7 ns)
256kB Range : 12.3 clk (~3.7 ns)
1MB Range : 12.3 clk (~3.7 ns)
4MB Range : 14.7 clk (~4.5 ns)
16MB Range : 8.8 ns (29.1 clk)
64MB Range : 8.7 ns (28.8 clk)​

RAM Bandwidth Int Buff'd iSSE2 : 7267 MB/s
RAM Bandwidth Float Buff'd iSSE2 : 7322 MB/s

details
Int Buff'd iSSE2 (Integer STREAM) Results Breakdown
Assignment : 7116MB/s
Scaling : 7116MB/s
Addition : 7404MB/s
Triad : 7435MB/s
Float Buff'd iSSE2 (Float STREAM) Results Breakdown
Assignment : 7190MB/s
Scaling : 7166MB/s
Addition : 7416MB/s
Triad : 7517MB/s
Warning 5010 : Cannot use Large Memory Pages due to lack of privileges.​

So, it would appear to me that 916.7Mhz @ 1T and 1066.7Mhz @2T are pretty effectively equivalent. (EDIT: It also appears both are rather better than the Sync mode result @ 733 4-4-4-12-1T (17TRC) w/2.2v.) I have decided to stick with my DDR2-1066 setting because it needs rather less voltage to remain stable. Unless anyone knows that mem-controller or termination voltage changes would lower the amount of vDIMM I need to use with the 916.7 setting?

Again, what does everyone think of these results based on these different overclocks?

Have you tried testing 1:1 synced vs out of sync but running faster?

jmackay said:

Have you tried testing 1:1 synced vs out of sync but running faster?

Click to expand...

Well, I need "unlinked" to get the 1066 or 916, and 800 is "linked" with the multiplier on "auto". Synced would only be 733, but that is a good suggestion. I will try that out and edit in other numbers. I will post again when I have made the edit.

EDIT: wrong info on RAM speeds @ BIOS settings. Just had a horrible time trying to run @ 733 with low latency settings, even though 3-3-3-9-1T (16TRC) booted and loaded windows. One more time...

Betrayer00GT said:

Well, I need "unlinked" to get the 1066, 916, or the 800 speeds I have tested at. That is a good suggestion, however. I will try that out and edit in other numbers. I will post again when I have made the edit.

Click to expand...

Cool thanks =)

New numbers for Sync mode are up.