On Sunday 24 November 2002 15:55, you wrote:
> I'm giving my brother's family a new computer for christmas.
> He'll buy it from a local (to him) 'white box' pc store and I'll
> pay for it. I am a little concerned about performance because
> the pc will probably be running GIMPS and I'd like to get my
> money's worth. It's easy to request a P4 in the 2.0-2.5 range
> and 256M-512M of memory but I've read of the bottleneck caused
> by slow memory and the bus between memory and cpu and I don't
> know what to specify or how to evaluate components in this area
> or measure performance after the pc is built.
>
> Any comments or suggestions?
Well - one of the key things with P4 systems is that the processor needs to
be properly cooled. If it isn't, the reliability will probably be OK, but the
performance will suffer as the processor goes into thermal throttle mode.
Unfortunately many "fashion" systems come in unreasonably small cases with
grossly inadequate ventilation, and an underspecified heat sink. Most users
never notice that the system is throttled, because even at quarter speed, a 2
GHz P4 is more than powerful enough for everyday tasks like word processing,
even using M$'s mega-bloated packages. Also, shifting sufficient air to cool
a P4 (or a high-end Athlon) properly means either a large, heavy and
expensive heat sink, or a noisy fan.
Basically my advice would be to go for build quality rather than raw
performance. If the thing is properly built, you will at least be able to do
something about any deficiencies.
I would reject out of hand any package containing peripherals which are
designed to work only with Windows, or which has Windows pre-installed with
only a "system recovery" CD rather than proper installation media. I'd far
prefer to take a system without Windows bundled at all, but M$ tries to make
life miserable for system builders who try to avoid the "Microsoft tax".
>
> I want them to have a fast machine but not on the bleeding
> (expensive) edge.
The problem here is that most "big name" systems builders keep changing the
important components (motherboard, graphics card etc) to suit their profit
margins and stock availability. You will find apparently identical systems,
with the same "top line" specification, are quite different inside and may
have very different performance.
So ... look for something that at least tells you what the mainboard chipset
is. This will give you a good indication of the performance _potential_ and
upgradeability of the system.
Personally - although this is distinctly unfashionable - I far prefer Rambus
memory - so far as GIMPS is concerned, a 2.53 GHz P4 using PC1066 Rambus
memory (implying the i850E chipset) will outperform _any_ system up to 2.8
GHz using DDR memory. The point here is that the total memory bandwidth of
the Rambus system is 4200 Mbytes/sec, whereas even using 400 MHz DDR memory
(just as rare & expensive as PC1066 Rambus memory) you are only going to get
3200 MBytes/sec.
If you're forced to a DDR based system, then look for the Intel 845PE
chipset. (This also supports the new P4 processors up to at least 3.06 GHz
with hyperthreading support enabled). With chipsets using DDR, there is
potential for inefficiency by using slow memory - e.g. KT400 chipset should
always be used with 400 MHz memory (PC3200), KT333 with 333 MHz memory
(PC2700) etc. This is because the "gearchange" caused by using slower memory
than the chipset supports kills performance. Installing faster memory than
the chipset supports is OK (except that Rambus systems supporting only PC800
RDRAM do _not_ work with PC1066 memory) but not often done for reasons of
cost.
The problem here is that few "big name" manufacturers will tell you the
specification of the components have gone into a system, and even fewer sales
assistants in the retail stores where they're sold will understand
intelligent questioning. (They _may_ understand raw MHz, disk capacity,
monitor size etc., but that's about the limit of what you should expect.)
If you really want performance, and are prepared to cut back on things you
don't need (superfluous peripherals, bundled software etc), then it is
practically essential to "roll your own", or (at a premium) go to a small,
specialist systems builder armed with a specification. Building the thing
yourself is satisfying, too.
>
> Other than GIMPS I'm sure my nephew will be the heaviest load
> when he plays games on the new machine.
So you want a darned good graphics card ... a weak graphics card will kill
games performance much more than a poor mainboard/processor/memory
combination. Many games players also insist on a good sound system.
>
> I think I should also request the video card has all of it's own
> memory, right? I don't want the video to share the main memory
> for performance reasons, right?
Definitely. The only reasons for integrated graphics are reduction in
component costs & space saving; the performance hit is substantial. Worse,
with systems built with integrated graphics, it's often impossible to upgrade
the graphics with a plug-in card, because the slot isn't there, or there's no
room in the case, or the power supply won't cope. If you _must_ have a very
compact unit (laptop system) then integrated graphics makes sense. But not in
a desktop type system.
Another point here is that high-end graphics cards have at least 64MBytes of
their own memory on-board - in fact 128 MBytes is becoming common. Taking
that out of your system memory can, on its own, affect performance if you're
marginal to start off with.
Regards
Brian Beesley
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