4 GIG of RAM drops speed to ddr 333 instead of 400

[satyr451]

I've recently run into a problem with my a8n-vm csm motherboard. First my system became really unstable, and I traced the issue to 2 sticks of faulty memory. When I got the replacement ram from Corsair and I added it in everything was stable again but my memory will only run at ddr333, instead of ddr400. If I take 2 gig out, it goes back up to ddr400. I'm wondering is something is screwy with my mobo...anyone else seen anything like this? Is this a limitation of the board with 4 gigs of ram or something?

I could swear that when I initially set up the system that it ran 4gig at ddr 400 speeds.

System Specs:
Apevia (Aspire) X-Qpack case.
Asus a8n-vm csm
Athlon x2 4400
ATI Radeon x1800XT
4 gig corsair XMS (2x Twinx2048-3200c2pt)
2x western dig 250Gig HDs RAID0
Antec truepower 500watts

 

[Admiral_Cecil]

Hello,

If you want to run at DDR400, then you can only do it with 2x 256, 2x 512, 2x 1gb, etc.

Otherwise, it is common on AMD 939 systems to default to DDR333 if you use 4 sticks. Better to go with two sticks so you can run more efficiently and at 1t.

 

[Multiplectic]

I had the same issue with my mobo. It's due to the ODMC the Athlon 64 has.
All I had to do was to set the clock and timings manually, and it was ready to go. DDR400 @ 2.5-3-3-6 2T, and that's the best it can do (cause mine aren't Corsair modules ).
If you have 4 sticks, 2T Command Rate is the only option. Again, ODMC limitations. It will only be ~5% slower than 1T, and it isn't really noticeable (at least in my case).

 

[4745454b]

I'd like to point out one more thing. Buying two more sticks of ram and adding them in won't "fix" the stick that was bad. That stick(s) should have been pulled. It was bad at DDR400 1T speeds, but now fine running slower at DDR333 2T speeds.
If you had a bad stick, I would pull it/return it. OR do what you did, which is run it at a slower, more stable speed.

 

[maury73]

It's absolutely normal. As it was said in many posts in the past, it's very difficult to found a mobo that can run 4 DIMMs at maximum frequency, in fact the very first dual channel mobo had 3 slots only, thus allowing only 2x dual channel config.
This due to the longer PCB tracks that cause signal corruption, and you can't resolve this with a simple BIOS upgrade. The BIOS could remove the frequency limit, but can't avoid system instability that come out for sure with unbuffered DIMMs.

This is why server class mobo requires buffered DIMMs: they have up to 8 slots, because buf DIMMs assure better signal integrity and reliability.

 

[Preecher]

Its a "bug" in the memory controler for AMD's. If you want more than 2 gig of ram, then it runs at the slower speeds. I dont know much more than that but this subject has been discussed a few times before in this forum... which is where i gleened the statement in my first sentence.

Multiplectic seems to have found a partial workaround tho.. perhaps try his solution?