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SubjectRe: quad ppro Compaq proliant 5000 problems with 2.1.106-ac4 was: Re: Any SMP people out there with SCSI CD ROMs?
On Thu, 25 Jun 1998, Chris Pirih wrote:

> >> > Robert HYATT wrote:
> >> > > I ran the matrix multiply benchmark... with 1, 2, 3 and 4
> >> > > processors.
> >> > > The numbers I got were 52 seconds, 59 seconds, 66 seconds and 73 seconds

At least you know matrix multiply is totaly blocked on main memory,
otherwise you might see 1/4 the performance with 4 processes.

> Look everybody, it's very simple. 1 copy of the program takes 52
> seconds. 2 copies of the same program running at the same time take
> 59 seconds each. 3 copies take 66 seconds, 4 take 73. Each process
> runs on its own CPU, but when several of them are running each takes
> a little longer because they contend for the slow main memory, even
> though each process has a CPU all to itself.

This is one of the drawbacks with ppro's is that their chipsets,the 450gx
and 440fx have about half the memory bandwidth of the p2's lx chipset with
the bx chipset providing slightly higher throughput than that. Of course
450gx is the only way to go for 4 processors on a pc (for the next couple
of days anyway) until the 450nx and the slot2 p2 make their entrance. see
the discussion about this in the beowulf list about 6 months ago.

http://cesdis1.gsfc.nasa.gov/hypermail/beowulf/beowulf.9712/subject.html#start

or more specifically:

http://cesdis1.gsfc.nasa.gov/hypermail/beowulf/beowulf.9712/0067.html

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