Performance problems with dual channel DDR memory

[Robert L Cochran]

Are you using the very latest BIOS for this motherboard?

What brand and model number is the memory and does Intel say that 
brand/model of memory offers acceptable dual-channel performance in that 
motherboard?

My MSI K8N Neo2 (MS-7025...it's a Socket 939, AMD Athlon 64 board) came 
with a Test Report booklet which is a valuable reference for me. It 
lists brands and models of memory that worked in dual channel mode. I 
opted to use a no-name or 'generic' brand of DDR memory. This performs 
great at the slower 2T (DDR 333 instead of DDR 400) timings in dual 
channel mode. I was able to get 2 Gb at the prices newegg.com offered 
me. It was a huge savings compared to Crucial Ballistix memory, for 
example. I don't care about the performance, as long as it works.

For your purposes, if memory performance is important, you need to be 
very conscious of the motherboard BIOS version, and the memory brand and 
model number and the timings associated with that model. And also 
whether it is certified for use in that motherboard by Intel. I think it 
is more a hardware-centric thing than an OS thing. But I could be wrong 
there.

Bob

fedora at geniushealth.com wrote:

> Has anyone experienced performance problems when using dual channel 
> DDR memory?
>
> We are trialling an Intel 915 GAGL motherboard, using two sticks of 
> 512 DDR memory, arranged as dual channel memory. Performance drops by 
> 2 to 5 fold slower when both banks of RAM are installed. When one bank 
> is removed, performance raises back to an acceptable level.
>
> Are there any known problems with RedHat Fedora and dual channel 
> memory? Are there issues in the kernel / patches supplied, that makes 
> the system non-performant when using dual-channel memory? (Possibly 
> also linked with a hyper-threading P4 CPU?)
>
> Has anyone else got acceptable performance from using dual channel 
> memory with Linux on Fedora? (Either an alternative AMD based system, 
> or other?) We'd be very interested to hear.
>
> Our test system
>   Motherboard:   Intel 915 GAGL
>   CPU: P4 3GHz with hyperthreading
>   RAM: 2 x 512Mb DDR (and 1x512Mb for non-dual channel tests)
>   OS: Linux Redhat Fedora Core 3
>   Kernel: 2.6.9-1.667smp (standard kernel supplied by Fedora Core 3 
> install).
>
> Many thanks in advance for any advice / suggestions anyone can offer.
>