[clug] OT: DDR RAM and FSB speed

Duncan Roe duncan_roe at acslink.net.au
Thu Jan 27 21:13:02 GMT 2005

Hi Darren,

Just checking - are you saying DDR400 & PCI3200 are different?

I was told emphatically by the PC shop that they were the same, but I'm having a
problem with my dual Opteron - BIOS only sees 3.5G with all 4 sticks in but sees
2G with any 2 in. Tech support said to upgrade to latest BIOS which I did, but
the problem persists.

Cheers ... Duncan.

On Thu, Jan 27, 2005 at 09:09:41AM +1100, Darren Freeman wrote:
> On Mon, 2005-01-24 at 13:57, Steve Walsh wrote:
> > He's Close, but he's also very very wrong.
> >
> > DDR400 is hit twice in a clock cycle, so whilst it is hit only at 200Mhz,
> > due to the fact it loads twice per clock cycle it is effectively running at
> > 400Mhz. He's been caught by the SDR/DDR conversion.(DDR266 runs at 133, DDR
> > 400 runs at 200, but 200Mhz is a lower number than 266, so therefore it all
> > works out in his head) Thankfully, the board in question should auto detect
> > that it has slower ram and run accordingly.
> I think you missed the question and I think he knows the SDR/DDR
> convention.
> Brett asked for PC3200 RAM and got quoted PC2100 RAM. He wants to know
> if the motherboard will interleave two sticks of RAM to make up for the
> fact that one stick is slower than the FSB. I don't think he wants his
> shiny new Dual Xeon to detect the slower memory and run slower.
> Have fun,
> Darren
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