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AMD on-chip memory controller limitation?


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Hello again,


I've been reading countless posts about people not being able to reach ddr 400 with 4 x 512 mb (2gb) set-ups. They usually end up going to ddr-333 with 2t timings.


From my understanding it usually is because of the memory controller not being able to handle it. AMD's memory controllers are on the processor chip, and some people can not get to ddr400.


I'd really like to add another gigabyte of TWINX1024-3200XLPRO to my board, but I'm nervous if my setup will handle the second gigabyte at ddr400. I had heard rumors that the newer chips from AMD were able to handle it, but I don't know. So here's my setup.


Abit Fatal1ty AN8 SLI

1 GB TWINX1024-3200XLPRO ddr slot 1 and 2 @ ddr 400 (2-2-2-5 at 2T) - 1T for me is crash city

AMD X2 4400


(the rest of the specs, if they matter are:

thermaltake 680 psu

2 bfg 7800 gtx,

74gb wd raptor

80 gb media bin -crapdrive


So I'm wondering, with the above setup, will DDR 400 on all chips be possible? (even if it's at 2T, thats fine).

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I looked through the manual (imagine that) and I found a bit more detail, but I have another question.


It looks like if these are 'single rank' chips then they can run in ddr 400. is the twinxlpro 3200 single rank?


Does anyone know if they are single rank or double rank? What does that mean anyway?


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To be more clear myself...


The command rate at anything above 2 modules (sometimes more than one) will be 2T because of a memory controller (on chip) limitation of the A64 CPU.


There are single-rank 512MB modules available, but the 3200XL modules (based on Samsung TCCD IC's) are double-rank.




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Well it's either manchester or toledo. The one i have is the one with 2 mb cache (1 per core).


Anyways I bought another set of twinx 3200 xlpro to bring me up to 2 gigs. The bios lets me run at ddr 400, i was fine at that for quite a while, then it turns off. Then it stopped starting windows, then after a while my windows install got corrupted, whee.


I know that when I change the voltage to 2.75 on the ram, it sucks and won't start windows, never would. When I do memtest should I have it at 2.75? or at 2.6?


As far as I can tell, so far, I'll never do abit again.

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In a previous thread I posted how my machine would just die when running directx games or nvidia demos. You mentioned to me that the power supply might not have enough gusto to power those two 7800 gtx's. I work with computers every day - all intel, not enthusiast grade. This is like night and day and I was really reaching for ideas. The ram seemed easy to blame, there's a lot of confusion out there regarding ram/motherboard/amd (well if you're new to amd like I am).


Well I must admit I should have took your advice earlier on regarding the power supply. I humbly appologize for not learning my lesson earlier on.


Today I took one video card off the PCIe power cord that from the PSU and put it by itself, on it's own set of cords from the PSU. I had assumed that it was the ram's fault. -- not the case. memtest86 shows the ram PERFECT @ 2-2-2-5 (x2 4400 forces 2t, which is fine) and 2 GB now. Heck! The way I had it before it didn't run this long at 1 gb stable. Go Corsair :) I do love how the xlpro's glitter and I am VERY happy atm.


Now that I've gotten away from daisychaining the two cards off the same connector, this machine is just zipping along without any issues (knock on wood so far)... but it's been two hours running the app that usually would ccrash it within 10 minutes before.


I owe you much beer. Thanks so much, you were dead on.

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