🚀 go-pugleaf

<posted and mailed>

On Wed, 03 May 2000 00:56:01 GMT, Lisa <lisse@saintmail.net> wrote:
>Pardon me for asking questions that all - except me - already know -
>
>What are the differences of Xeon processors from Pentiums?

	Well, there are a couple things to note.  First, there are two
basic types of Pentium II/Pentium III processors as well as two basic
types of PII/PIII Xeons.  All PIIs and the older PIIIs (up all those
up to 600MHz without an "E" at the end, ie the PIII 600 and 600B, but
not the 600E or 600EB) used 512KB of off-die cache memory.  Cache
memory is very fast ram that is used to store frequantly used data.
On these older PIIs and PIIIs, this cache came in the form of chips on
the processor module inside the cartridge, and it ran at 1/2 of the
processors speed (ie the 400MHz PII had 200MHz cache, 600MHz PIII had
300MHz cache, etc.)  The newer PIIIs (the 533EB, 550E, 600E, 600EB and
all faster PIIIs) have 256K of cache right on the same die as the
processor, and it's running at full processor core speed, making them
a bit (10%?) faster at the same clock speed.

	So, now where do the Xeons enter into things?  Well, the older
Xeons (400 through 550MHz) were based on the same design as the older
PII/PIIIs with off-die L2 cache.  The only difference between the
chips were that the Xeons had full speed off-die cache, and in many
cases more of them (Xeons were available with 512K, 1MB and 2MB of
off-die, full speed L2 cache, vs. teh 512K of off-die half-speed cache
for the PII/PIIIs).  These chips also came in Slot 2 packages which
were larger then the Slot 1 package which the regular PII/PIIIs came
in, and they could be used in 4 or 8 way SMP systems, while the
PII/PIIIs could only be used in dual processor systems.

	Now, here's were it gets a bit dirty.  The new Xeons, starting
with the 600MHz parts and all faster ones available at this time, are
just regular PIIIs in a different package.  They have only 256K of
cache, they are not designed for 4 or 8 way SMP systems, etc. etc.
There's absolutely no difference between a 667MHz PIII and a 667MHz
PIII Xeon.

As a bit of a side note, I should mention that Intel will be bringing
out new large-cache, 4 or 8-way SMP capable Xeons at some point in
time during this year.  These chips, when released, should once again
restore all the advantages (and perhaps more) that the old Xeons had
over PIIIs.

>What are the benefits of using Xeons instead of plain vanilla Pentiums?
>
>Is there a speed difference - even with the same MHz rating?

	With the older Xeons, there was a performance difference
between them and the regular PII/PIIIs of the same speed, especially
with the larger cache versions.  Just how much of a difference
depended on what your applications where like.  For most desktop users
the difference was negligible.  For some servers it made a pretty
significant difference.  That, combined with the ability to use 4 or 8
processors in one system made them a much better solution for servers.
Now, there's no real advantage at all to the Xeons.

>What are the strong points of Xeon, as compared to Pentium?
>
>I heard some talk about "stability" of Xeon, but what does that means? I
>thought most times the computer hangs is because of the softwares'
>(read: OS) faults, very seldom we see hardware failure causing whole
>system to hang.

	I'd guess that over 90% of all system crashes are caused by
software, or at the very least the drivers for the hardware, and
that's assuming a decent operating system.  In the case of Win9x, that
number would be just about 100%.  The processor makes virtually no
difference when it comes to stability unless the chip is dead.  The
componants that affect a system's stability the most are motherboards,
video cards, network cards and sound cards, and there it's almost
totally an issue of drivers rather then the hardware itself (though
obviousy if you buy el-cheapo hardware for a server, you most likely
will run into hardware stability problems).

>In SMP environment, does Xeon shine better? How about uni-proc
>environment? How about clusterred environment?

	In the case of the older PII/PIII Xeons, they were better in
SMP systems, first because with the ability to work with 4 or 8
processors in a system instead of just 2, but also because the faster
and larger cache meant that the processors were less dependant on main
memory, which is shared between all processors in an SMP system.
Again, for the new Xeons, this difference no longer exists.

>Is there anywhere in the Net where I can get the info?

	I remember Tom's Hardware did some testing on them a while
back for desktop use (ie "office" applications, games and a few other
things) and found that there was virtually no difference.   Of coures,
that was a kinda pointless review since the Xeon was totally not
designed for this sort of purpose.  Still, you could read up on it if
you like, it's somewhere on www.tomshardware.com.  Other than that,
you could check the Spec numbers for these chips at www.specbench.org
to get some comparative results.  I seem to recall that the Xeons did
pretty well at Spec's webserver benchmark.

Hope this helps!

Anthony Hill
hilla@uoguelph.ca