A8N32-SLI: Memory Tweak

[lopri]

My main rig is housed on A8N32-SLI now, and while it was much frustrating to work with it, ASUS boards seem to like the 1G sticks better than DFI boards do. Now, I do not have much experience in memory tweaking and I generally believe it's not worth the time and effort, there was an incident that got me into this thing and to my surprise, memory tweaking wasn't too hard with this specific board.

Reason? The board itself has a superb BIOS setting and it sets very efficient timings under most "Auto" option. So my general advice on memory with this board is - leave it alone. Said that, my goal with the set I have (OCZ PC3200 Titanium 1G x2) was to tighten up things as much as possible @2-3-2-5-1T timing. Due to my CPU (Opteron 165)'s multiplier limitation (~x9), as well as limited dividers the board provides, this seemed to be only sensible choice.

Setup:

AMD Opteron 165 @3GHz
OCZ PC3200 Titanium 1G x2 (up to 220MHz @2-3-2-5 / up to 250MHz @2.5-3-2-7 / up to 265MHz @3-3-3-7)
ASUS A8N32-SLI BIOS 1103

The improvement is measured by Super PI 1M. It's by no means a real-life application, but like everybody else here, I have a "real" life, too, and can't waste time running hours of game benches. Also, to my knowledge, Super PI reacts quite sensitively to memory configuration so I figured it'd do the job for this purpose.

Note: The OCZ RAM is known to utilize the Infineon CE-5 ICs. So if your 1G sticks have different ICs, things can be very different. Also, even if your sticks are Infineon, every sticks are different - this result is just an example and don't PM me because your rig doesn't boot up after copying the setting.

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[lopri]

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My recommendation in the order of superiority:

1. Leave things to the BIOS. It'll take care of things much, much better than you expected. (even better than DFI boards with these Infineon sticks)
2. Make minimalistic changes according to your CPU OC. e.g. Dividers, the Big 4s (2-3-2-5) and 1T
3. Now here is what I did. Will show Before/After followed by respective Super PI 1M results.

Following is the 'Before' setting: <-- This is what the BIOS set after I set 2-3-2-5-1T / 2:3

CAS Latency (CL) 2T
RAS To CAS Delay (tRCD) 3T
RAS Precharge (tRP) 2T
RAS Active Time (tRAS) 5T
Row Cycle Time (tRC) 16T
Row Refresh Cycle Time (tRFC) 19T
Command Rate (CR) 1T
RAS To RAS Delay (tRRD) 7T
Write Recovery Time (tWR) 2T
Read To Write Delay (tRTW) 6T
Write To Read Delay (tWTR) 1T
Write CAS Latency (tWCL) 1T
Refresh Period (tREF) 133 MHz 7.8 us
DQS Skew Control Disabled
DRAM Drive Strength Normal
DRAM Data Drive Strength 4 (No Reduction)
Max Async Latency 9 ns
Read Preamble Time 7.0 ns
Idle Cycle Limit 16
Dynamic Idle Cycle Counter Enabled
Read/Write Queue Bypass 16
Bypass Max 7
32-byte Granularity Disabled

And the 'After' setting:

CAS Latency (CL) 2T
RAS To CAS Delay (tRCD) 3T
RAS Precharge (tRP) 2T
RAS Active Time (tRAS) 5T
Row Cycle Time (tRC) 7T
Row Refresh Cycle Time (tRFC) 11T
Command Rate (CR) 1T
RAS To RAS Delay (tRRD) 2T
Write Recovery Time (tWR) 2T
Read To Write Delay (tRTW) 1T
Write To Read Delay (tWTR) 1T
Write CAS Latency (tWCL) 1T
Refresh Period (tREF) 133 MHz 15.6 us
DQS Skew Control Decrease Skew <---
DQS Skew Value 0
DRAM Drive Strength Normal
DRAM Data Drive Strength 4 (No Reduction)
Max Async Latency 9 ns
Read Preamble Time 7.0 ns
Idle Cycle Limit 256
Dynamic Idle Cycle Counter Enabled
Read/Write Queue Bypass 16
Bypass Max 7
32-byte Granularity Disabled

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[lopri]

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Readings were taken from Everest Home Edition, and changes I made in the BIOS are bolded. Here is the list of the tweaks in the order of importance, IMO.

1. For some reason the BIOS sets tRTW @6T, which is way off. So that's the first thing I changed.
2. Try to lower tRC/tRFC. I'd start from 12/16, respectively, and lower them step by step.
3. Write to Read Delay (tWTR)/ Read to Write Delay (tRTW) - try setting these values the same. I'd start at 3/3 then 2/2, and finally 1/1. 1/1 might be unreachable if your memory is overclocked past certain MHz.
4. tREF - definitely @15.6us
5. Idle Cycle Limit set to 256
6. Read Preamable / Max Async Latency Combo - didn't really see any difference from default 7ns/9ns. I'd leave it at that.

Result:
Before
http://img160.imageshack.us/my.php?image=a8n32default3fh.jpg
After
http://img96.imageshack.us/my.php?image=a8n32tweaked6fs.jpg

VDIMM was at 2.70~2.75V. I set it at 2.70V at the beginning and raised it to 2.75V sometime after, but I do not remember when. But raising past 2.80V did absolutely nothing for this set. I'd assume the same for other 1G Infineon sticks. These settings were stable through 6 hours of Prime95 LargeFFT. I didn't really check the 3D stability due to the fact my current card is a 6200TC, but once my 7900GT gets here I will report back. Still, my general opinion on memory tweaking still stays the same: It's not worth the time (and frustration). I just had to know what it was and I tried to make it quick (2~3 days). If you're the type who'd have fun running Super PI (or Sandra) 24/7, then maybe it's your thing. But otherwise, save the headache and play some games, or get some booze!