4x512 memory divider issue

[silrais]

Hardware:
~~~~~~~
Athlon 64 x2 3800+
2GB (4x512) Mushkin 3200 RAM
MSI K8N Neo4/SLI

With all four dimm slots populated, my motherboard resorts to running the RAM on the 166 divider (333MHz). Doing this, I can overclock my processor to 2.4GHz without issues, but pushing the RAM much above 400 results in instability.

Changing nothing besides the divider, any attempts to lower it to 133 have resulted in the system being unable to pass POST. My question is, what's causing this, and is there a way around it? I believe it's due to the motherboard over-ride, but would like confirmation.

My HT speeds, RAM timings, and voltages are all within range.

 

[stevty2889]

Try the same divider with 2 sticks of ram and see what happens. I was getting some strange issues with dividers when using 4 sticks of ram, where for some reason a lower divider would run the ram way above it's rated speed..but not with 2 sticks of ram..

 

[silrais]

I actually just finished doing that.

Booting with two sticks will let me into Windows, but it's highly unstable. Prime95 fails after just a couple minutes. The only RAM timings I have manually assigned in the BIOS are 2.5-3-3-7. Everything else is set to AUTO.

I'm beginning to think the motherboard is assigning timings based on a 266FSB instead of native 400 timings, and therefore setting them much lower. This would cause near instant instability unless it was still running at 266, but with the HT speeds around 240-250, it's really around 333.

Setting all RAM timings back to AUTO, and HT speeds back to default levels, I booted into WindowsXP to run CPU-Z. At the 200 divider, timings were the same as I had manually assigned 2.5-3-3-7. At the 133 divider, timings were 2-2-2-7. This is what leads me to believe it's auto-assigning values based on divider speed.

I have no experience with TRRD, TRWT, TWR, TWTR, and TREF timings, so I don't know what levels to manually assign them to see if that will work.

 

[the cobbler]

the 133 divider is broken in the bios! no kidding...

I am using thee 1.6 bios and 133 doesn't post, all the other dividers are fine

try one of the 1.7x betas or mods, those are good versions and have a working 133, but lack the 120/140/150/180 dividers

 

[Shenkoa]

My 133 divider is strange, while it works it just does not do good for overclocking. As a general rule of thumb, never get 4 512 sticks of memory for AMD platforms.

 

[silrais]

Originally posted by: Shenkoa
As a general rule of thumb, never get 4 512 sticks of memory for AMD platforms.

A little late for that now.

I'm currently using BIOS version 3.7. Dividers for 120/140/150/180 aren't available unless I'm missing something. They would be tremendously useful.

 

[Shenkoa]

My mobo is kindof like yours, I have dividers for 100/133/166/200

 

[the cobbler]

Originally posted by: silrais

Originally posted by: Shenkoa
As a general rule of thumb, never get 4 512 sticks of memory for AMD platforms.

A little late for that now.

I'm currently using BIOS version 3.7. Dividers for 120/140/150/180 aren't available unless I'm missing something. They would be tremendously useful.

oops my bad
see you have the MS-7100, I have the MS-7125 (non-sli)
still, some versions of the bios have 120/133/150/180 dividers
the 3.0 official does for sure, you might have to hunt around to find which newer bios also have the dividers

if your RAM is single-sided, 4x512 is fine, you just won't be able to run 1T but still will be DDR400

 

[bigpow]

I'm able to drive 4x512 at 1T, but at 100/200 divider
Anything higher and it would lock-up, regardless of voltage & timing.

But, 4x512 at 2T is a lot faster in real usage than 2x512 at 1T, at any timing!

 

[Shenkoa]

That depends on the application of course, but I would not expect games to perform better at 2T.