[Beowulf] Memory for Tyan motherboards

[Bill Broadley]

On Mon, May 16, 2005 at 02:27:45PM +0100, Frank Scott wrote:
> I am involved in specifying some machines for running finite element
> analysis. I am proposing to use dual Opteron 250s on Tyan motherboads
> with 16GiB of PC3200 ram.

Which tyan motherboard?  One with 8 Dimm slots?

> I've had it suggested that Tyan only support PC2700 memory when 16GiB is
> used. Does anybody have any experience with Tyans and 16Gib of ram?

My understanding is that the older opterons including the B* C* revisions
will run 4 dimms per cpu at PC2100 or PC2700 when they are doublesided.
PC3200 would "work" but only provide the lower performance.  So you
would be best off buying the PC2700.

Do you expect to be memory bandwidth limited?

> If I use PC2700 instead of PC3200 will the drop in performance be
> significant?

Depends entirely on the application.  If it's cache friendly no.  If it's
latency sensitive mostly no, if it's bandwidth limited then yes.

The new E4 (90nm opteron single core) or E6 (90nm opteron dual core)
can run 4 double sided dimms at the full 400 MHz/PC3200 and would give
you the best of both worlds (assuming you can find PC3200 2GB dimms).

BTW, E4 opterons as slower than the opteron 252 have been announced,
but seem pretty rare so far.  To the part numbers go to:
	http://www.amd.com/qrgopteron1

Then filter for E4

Of depending on your budget you might consider getting a quad, you could
buy much cheaper dimms and get double the processors and memory bandwidth.

So basically with 130nm opterons buy PC2700 if it's cheaper, buy a 90nm
opteron and PC3200, or get a quad and PC3200 1GB dimms.

-- 
Bill Broadley
Computational Science and Engineering
UC Davis