>32GB memory with Xeon ?

Ken Gunderson kgunders at teamcool.net
Tue Dec 26 14:57:15 PST 2006

On Wed, 27 Dec 2006 05:08:36 +0900
Hiroharu Tamaru <tamaru at myn.rcast.u-tokyo.ac.jp> wrote:

> At Tue, 26 Dec 2006 10:44:40 -0700, Ken Gunderson wrote:
> > 
> > On Tue, 26 Dec 2006 23:07:58 +0900
> > Hiroharu Tamaru <tamaru at myn.rcast.u-tokyo.ac.jp> wrote:
> > 
> > > Hello list,
> > > 
> > > Is there any limit on the amount of memory that can be used
> > > with FreeBSD 6.x/amd64 ?  I found that FreeBSD/ia64
> > > currently has 2GB limit.  I was wondering how amd64 is like.
> > > 
> > > Specifically, I am thinking of a Dual-core x Dual-processor
> > > Xeon 5160, with 5000P chipset and something like 40GB of
> > > RAM.
> > 
> > Any particular reason you've ruled out AMD platform?  I know some folks
> > who've done some big enterprise class SAP machines based on AMD and
> > Linux. Not 100% sure but I think I recall AMD8111 and AMD8131 chipsets
> > and boards fully loaded with 32GB.
> No, I haven't ruled it out yet.  In fact, I've just started
> looking around.
> My usage is computation, and previous experiences showed
> that for our workload, the main memory bandwidth gave the
> largest influence on speed (it has a very low data
> locality).  We have IA64 system running Linux as well (it's
> running Linux b/c we have large memory there too), but
> hearing that recent Woodcrest Xeons can have upto 21+GB/s
> bandwidth to the RAM, I got interested and started seeking
> around hardwarewise and softwarewise for possible options.
> Do you have any advice/comments in this regard for AMD
> platform too?

I personally don't have any recent experience with anything that large
and when I did it was on "big iron".  I've been sold on the AMD
platform for the past couple years, especially for server usage.  AMD's
approach to integrating the memory controller w/the cpu has been a big
win for them as they've been kicking Intel's butt as of late.  But
perhaps the Woodcrest will be Intel's savior.  But then again as soon
as Intel seems to do a bit of "catching up", AMD releases their latest
and greatest.  Check the "Roadmap" at amd.com.  Quad cores are due
to be out 2nd quarter of 2007 and many current am2 generation boards
will supposedly be able to support them after a BIOS flash. I say
supposedly because such was also "supposed" to be the case with the
single to dual core.  In some cases it worked and others not.  I think
mainly a matter of mainboard vendor.

Issues you can run into with AMD platform often have to do with
particular chipset used. The 8111 and 8131 are old but well supported.
I think they max at 32GB though and only DDR1, not DDR2.  Research
anything using nVidia* carefully.  Fwiw, I've never been favorably
impressed w/Serverworks based board, even on i386.

Others here will be able to provide more, but I suspect you'll get more
response after the holidays.


Best regards,

Ken Gunderson

"The course of history shows that as a government grows, liberty 
decreases."  (Thomas Jefferson)

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