[linux-help] Re: Dual processors

[james <james@xxxxxxxxxxxxxxxxxx>]

On Friday 09 August 2002 13:51, you wrote:
> For example, running two instances of Setiathome, running
> X, surfing the web and ripping/recording cds. All at once,
> without a burp one. I can easily have more concurrent processor
> activity occurring with Linux than with Windoze on the
> same machine
>
> Perhaps not the greatest example, but I've been very pleased
> with Linux and SMP.
>

For an example: I had some wav files from a cd sitting around on the hard 
drive, and I wanted to make compressed formats (ogg and mp3) of them today 
(box is dual P3-800). I fired up oggenc and lame and was doing things 
(browsing web and playing mp3s all while it was encoding, and it did not seem 
to slow down at all. (running top showed oggenc using mostly 73% and lame 
using 99%, and rest of system using the rest (values of one cpu so 200% is 
use of both at full) I venture to guess that is is due to process-afinity, 
where due to issues of swapping out caches a process is much more likely to 
always be scheduled on the same cpu (as opposed to whichever is open, which 
gets a slightly more even %cpu time, but is actually slower in general) which 
is better. 

Personally, I have more working 2-cpu machines than 1-cpu machines (I just 
got 2 celerons for a dual board on saturday) I find that they are much more 
responsive than single processor machines. Most of them I have gotten at very 
good prices (which means I lucked out) I personally would for a general 
purpose computer (for someone who doesn't multi-task as much as I do) 
recommend a single-processor machine because *generally* smp is much more 
expensive. If you have the money and are willing to spend it, I think it is 
worth it, however, check to see if other things in the computer should be 
improved first (RAM especially) unless you know you are going to be doing CPU 
intensive tasks. (generally smp is very expensive in the motherboard 
department, a very similar motherboard to the one I have (in the 2xP3) I saw 
on the internet for  $500+ which is more than the whole system cost, as I 
said, which was very lucky, that one did have onboard dual Ultra320 SCSI 
though.)

I would probably suggest AMD for dual processors (admittedly I am generally 
more favorable to AMDs) Recently people I work with built a dual-Athlon 
1700MP for a professor. I believe it ended up costing about $1700 (ignoring 
hard drive, scsi card, and monitor-which she already had, with a Gig of ram 
(DDR registered ECC = $$), and some extra goodies.) (I believe it was cheaper 
and the 1700 was an early estimate when considering some things. we didn't 
actually have to get (on-board SCSI (and some other things +200 over the 
motherboard without them), 1300 may have been the actuall. I would reccomend 
Tyan's sucessor to the S2460/S2462 series with the AMD 760-MPX chipset.

One important thing-most dual (and up) motherboards often require expensive 
memory (registered ECC for example, which is more expensive, and such) 
Generally it is standard (almost always) but in the price premium category. 
other things also contribute the high price-64bit PCI, onboard LAN, onboard 
SCSI and so on) AMD only explicitly supports Athlon MP chips for smp, though 
durons, and XPs have been used, but they may not, and the MPs cost much more.

Generally, advice is research it before you buy something so you know what 
you are getting into. In this case also realize there is a price premium, if 
you can afford it, and need it, it is probably a good thing to have. And as 
Jon Hall pointed out there is a certain geekyness to it. 

Feel free to correct me if anything is wrong.

James L.






> wayne
>
> At 09:49 AM 8/9/2002 -0500, you wrote:
> >For example?
> >
> > > My experience is that SMP really makes Linux multitasking
> > > shine brightly.
> > >
> > > wayne
> > >
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