[vox-tech] amd64

[Bill Broadley]

On Sun, Jan 18, 2004 at 11:11:01PM -0800, Peter Jay Salzman wrote:
> > Yeah, I've got 4 on campus (3 duals and a quad).  I've had no problems
> > with any of them.
>  
> excellent.  what motherboards are you running in the duals?

Riowords Arima and Tyan I believe.

> were they the "i saw a cool deal at frys" kind of purchase or the "i've
> been reading chipset roundups on anandtech for months" type of purchase?

Most of the important functionality is on the CPU now, so it doesn't
matter that much.  Do make sure that if your expecting maximum performance
you get > 4 dimms, otherwise your losing about halving your potential
memory bandwidth.

If course if your budget means single opteron or dual opteron with
one memory bus, the single bus might make sense.  I'm guessing a ballpark
for $200 ish for UNI boards, $250 ish for dual boards with a single
memory bus, and $400 ish for dual boards with dual memory busses.

> any motherboard recommendations for opteron SMP?

#1 anything with > 4 dimms
#2 tyan is good, but opterons are targeted at the high end (require registered 
   ECC mem etc) I suspect anything will work really well.

> i just read that opterons have a north bridge for each CPU and that
> there's no real common FSB.  i imagine that would have profound
> performance boost for numerical work.  and gaming.  :)

Indeed, my benchmarks show this, for instance on the P4:
http://www.math.ucdavis.edu/~bill/dual-p4-2.4-icc.png

Note how the 2 thread performance is LESS than the single thread performance
as the graph moves to the right (larger arrays not in cache).

With the dual opterons:
	http://www.math.ucdavis.edu/~bill/dual-1.4-4xPC2700-icc.png

Note how the 2 thread performance while not double is substantially
better than the single.  This is a relatively worst case (zero cache hits),
and shows very good scaling (I.e. 1.5 times faster is much better than
the p4's 90% as fast).  With most apps I'd expect performance to scale even
better than 1.5 when utilizing the second cpu.

> > For the security minded out there, the amd64 also supports additional
> > instructions to help prevent buffer overflows.
> 
> didn't hear that.  i'll have to read more about it -- this sounds OS
> dependent to me.

It is, but people are working on Linux support, openbsd support exists
for some architectures, but not X86-64 yet.  Microsoft has announcing
similar for both the x86-64 and the next generation p4 chip (not out yet).

> bingo.  :)   i was trying to find a quasi-respectable way of asking "has
> anyone run quake3 or UT on an opteron yet".
> 
> uhhh... i mean blender.   ;-)

Be warned, afaik, most 64 bit os's only run 64 bit native binaries with the
64 bit nvidia driver.  Thus a friend runs nwn on a dual opteron, but uses
opengl software emulation and still manages to get 60 fps with full detail
at 1600x1200.

At least for today using accelerated opengl, x86-64, and 32 bit games
may require running a 32 bit OS.

-- 
Bill Broadley
Information Architect
Computational Science and Engineering
UC Davis