[H-GEN] Compaq Proliant

Robert Brockway robert at timetraveller.org
Sat Jul 26 01:27:01 EDT 2003


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On Sat, 26 Jul 2003, Tony Bilbrough wrote:

> So I will keep looking for a faster/newer dual prcessor system, to play
> with. Perhaps an 800 Mz pair?

You might be able to pick one up 2nd hand.  Auctions are a great way to
pick stuff up[1].  Many times I've gone to the "Isles Love" Auction House
as well as the Public Trustee auctions and picked up bargains.

[1] Actually I have a feeling Tony has mentioned before that he's attended
comnputer auctions, but others may find this interesting.

> The 4 Gb one takes about 15 seconds to spin up, according to the bios.

Ouch.  I wonder if they are getting a bit old.

> One final qustion
> How much 'faster' is a dual 200 [total 400 Mz?] over a single 500 Mz [my
> current Humbug boxen]cpu.
> 5% , 10% or not at all?

An interesting question indeed.  How boxes compare is very much a function
of the work they are put to.  This is one of the reasons that benchmarks
are so useless.  The only real benchmark is the job you intended the box
to do :)

It is possible to speak in general terms though.  A 2x200Mhz box isn't
going to outpace a more modern 500Mhz box.  The newer box will likely have
a faster IO subsystem, etc.  In any case, even if the job being done is
cpu intensive, the 2x200Mhz box will be able to run 2 different processes
at 200Mhz.  With the help of threading it may be possible to run different
threads of a single unix process on both cpus.  This will be slower than
running these process(es) on your 500Mhz box, even ignoring issues
relating to IO speed.

Now let's compare the 2x200Mhz box to a single cpu 400Mhz box running on
the same hardware.  Unless you're regularly running multiple cpu intensive
applications on the box you're almost certainly still winning with the
faster single cpu system.  This is because most of the times that you want
grunt it's to run a single large app.

I have been told that Linux's performance on an SMP system is "near
linear" up to 8 cpus.  SMP is often being improved, and I just went
looking for something to backup my ascertion but I found nothing useful in
my quick search.  Anyway, near linear means a little less than linear.
This means that 2x200Mhz will not be performing quite as well as 1x400Mhz
(although the difference may not be noticable).  The difference comes from
both hardware (bus access) & software (kernel & userspace access) locking
issues.  Linux kernel 2.6 has finer grained SMP locking I believe, which
should help performance.

Bottom line is, unless the box is a server which expects to be running
multiple cpu intensive apps often you're better off getting one fast cpu
instead of 2 cpus half the speed.

Cheers,
	Rob

-- 
Robert Brockway B.Sc. email: robert at timetraveller.org  ICQ: 104781119
Linux counter project ID #16440 (http://counter.li.org)
"The earth is but one country and mankind its citizens" -Baha'u'llah

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