1T Command Rate Woes

[Somniferum]

I just bought a second stick of 512Mb Corsair ValueRAM to replace 2-256 sticks. So now I'm running 2x512Mb in dual channel mode ... nice performance boost. I had also hoped that by dropping from 3 to 2 sticks, I could run at 1T Command Rate -- which gives me a 20% memory bandwidth increase in Sandra.

Problem is, even with everything else at stock speeds, I cannot pass Memtest86 with Command Rate set to 1T. It always fails in the same place, right after the 14 minute mark. Basically the screen starts to fill with ##### characters and then it freezes. I had thought with 2 sticks of RAM, 1T should always be stable at stock speeds?

The strange thing is, I can run Prime95 for 10 hours at 1T with no errors, but Memtest86 fails at 14 minutes. At 2T, Memtest86 will run all night.

Memory timings are set at 2.5-3-3-8 (SPD). I also tried running the memory at CAS-3 instead of 2.5, as well as setting RAM voltage to "High" -- still failed just after 14 mins at 1T. I'm using ASRock BIOS version 1.5.

Any possible solutions, or am I just stuck running at 2T?

 

[BoboKatt]

With 4 DIMM slots have you tried the other two dual channel slots? Also it migth be something specific to your board as my original MSI Neo2 Plat (AGP) had no issues running 1T as long as I stuck to JUST 2 512 sticks in the appropirate dual channel slots.

You are saying you tried even at stock speeds so that rules out any sort of crazy oc or maybe SATA or other slot that might get oc'ed and cause instability. Also again I was using exactly that Corsair Value RAM and 2 sticks had no issues running 1T. I certainly wont say it's your power supply as that looks great. I am not familiar with your board so there might be some bios setting that migth be set to auto that screws things up but I cannot imagine that. Wish I could help more.

 

[dunno99]

You have to remember that memtest tests different things than prime. Memtest tests your RAM (and also some CPU + memory controller) while prime tests your CPU stability and some small amount of RAM (plus memory controller). All memtest does after bootloading and loading itself into memory is it fills all your memory with various values.

How about try swapping the memory modules and see if it still fails at 14 minutes? If it fails at a different time, then I would guess your memory is fubared. O/w, I'm guessing something wrong with the CPU's memory controller.

*spelling mistakes*

 

[Leper Messiah]

Originally posted by: dunno99
You have to remember that memtest tests different things than prime. Memtest tests your RAM (and also some CPU + memory controller) while prime tests your CPU stability and some small amount of RAM (plus memory controller). All memtest does after bootloading and loading itself into memory is it fills all your memory with various values.

How about try swapping the memory modules and see if it still fails at 14 minutes? If it fails at a different time, then I would guess your memory us fubared. O/w, I'm guessing something wrong with the CPU's memory controller.

try upping vdimm to 2.8. should be safe with CVR.

 

[dunkster]

You are one of many who can't run stably with 1T command rate with the Asrock board.

I can't either. I've tried a lot of BIOS versions (currently ocwbeta3), but none relieve this problem.

 

[Somniferum]

Thanks for all the suggestions. I tested each DIMM individually and they both pass Memtest86 at 1T with no problems. I also tried swapping them around, as well as using the other two DIMM slots, and in both cases Memtest86 fails as before. So it seems to me like the issue is running Dual Channel with 1T on this ASRock board. Maybe a future BIOS version will fix the problem.

As far as RAM voltage -- there are only two VDIMM options in the ASRock BIOS -- Normal and High. Setting it to High doesn't seem to make a difference with the 1T issue.

For the time being I'm switching back to 2T and overclocking the memory bus instead.