[CLN-list] Re: Re: A good PC hardware for CLN ?

[Joerg Arndt]

* Fabrice Marchant <fabricemarchant at free.fr> [Jan 26. 2006 10:47]:
> >    1. Re: A good PC hardware for CLN ? (Joerg Arndt)
> >    2. Re: A good PC hardware for CLN ? (Richard B. Kreckel)
> 
>   Thank you very much for your answers.
> > 
> > 
> > ----------------------------------------------------------------------
> > 
> > Message: 1
> > Date: Tue, 24 Jan 2006 16:33:40 +0100
> > From: Joerg Arndt <jj at suse.de>
> 
> > I invariably recommend AMD64 these days (socket 939).
> > 
> > [...]
> I'll follow you and the document : AMD64 !
> Are dual core useful ?

Well, you can run two processes in parallel.  Or two threads of one process.
Very few programs exploit the advantage of multi-core systems.
Single core processes may run a little slower on multi-core
systems (concurrent access to RAM, cache).
You can start in single-CPU mode if that ever matters
(boot parameter  maxcpus=1 with linux)

> 
> I looked at the prices (France) in this cheap store :
> http://www.ldlc.com/navigation/cat.html?sscat=140025&constructeur=C000000805&refParam1=PA069&refParam2=PA1112&paramValue1=Socket+939&paramValue2=
> 
> I noticed on this page :
> - AMD Athlon 64 3700+ - 2.2 GHz, Cache L2 1 Mo Socket 939 0.09 micron - Core San-Diego (version boîte) 259,01 euros and

fine CPU.

> - AMD Athlon 64 X2 Dual-Core 3800+ Socket 939 0.09 micron (version boîte) 338,99 euros.

with that you can start your parallel programming experience ;-)
Also: you can run a CPU hog all the time and still have (almost) full
performance with your compilations etc.

Note that two cores require a bigger power supply.
(dunno the difference though, 40Watts?)
If silence is a must check noise level beforehand.


> 
> > 
> > Message: 2
> > Date: Tue, 24 Jan 2006 22:45:39 +0100
> > From: "Richard B. Kreckel" <kreckel at ginac.de>
> [...]
> 
> Please, what does 64 bit userland mean ?
> Maybe recompiling your .cc sources for 64 bits will improve the speed too ?

Yes: e.g. CPU has a 64x64==128 bit integer multiply,
takes 4 mults on a 32bit system.

> Does g++3.3 is able to produce such code ?

yes

> Arbitrary precision arithmetic is a fun stuff and then very important to soften the hard life !

ACK

> I wonder if processor cache size is important for integer computations with CLN ?
> ( I focus on integers. )

_first_level_ cache seems to be more important, and
AMD64 has 64k data + 64k instruction (two way associative)
intel has a stinkin 8k.

second level: AMD64 has >=512k (and 16 way assoc.) that is enough.
Insane amounts of cache (e.g. intel itanium with 16MB(!)) indicates
that problems of the CPU are papered over.


> And RAM amount ?

take >=1G


> Dual channel ?

You want that (i.e. socket 939)!
Gives you the mem bandwidth which you positively want.
(must have two identical pieces of RAM in the machine).


> 
> Can we forget hard drive perfs, hoping a huge RAM avoids to swap ?

depends 8-)
If you must have processes that cause swap than create the swap
partition on a seperate drive.  And on the outer tracks.
Off the shelf SATA gives you 60MB/sec read performance.
Forget PATA btw.

But then, insane amounts of RAM never hurt.
Take 2G if in your budget.
Important: only buy quality RAM! (a 3 year warranty indicates quality).

all the best,
     jj

-- 
p=2^q-1 prime <== q>2, cosh(2^(q-2)*log(2+sqrt(3)))%p=0
Life is hard and then you die.