Bob said:
While looking for older CPU's to upgrade some P2B's, I've run across
Pentium II's, III's, and Celerons, and some designated as "XEON".
Can somebody give me a short description of what these terms actually
mean in terms of the processor's capabilities, speed, etc ?
As I'm no expert at this stuff, the differentiating factors I've
noticed are:
1) Amount of cache.
2) Whether processors are usable in dual or quad systems.
A Celeron is at the bottom of the pile. It still has a decent core
clock frequency, but a small cache. The one just before I bought
a PC, had zero KB of L2 cache. Users hated this "Celery" so much,
that the next Celeron had 128KB of L2, and Celeron processors since
then will be found with roughly that size cache.
A Pentium will have from two to four times the cache of the
Celeron. Frequently the core of the chip is the same as the
Celeron, as the engineering cost of neutering the core for
market differentiation purposes is too high. The extra cache
makes a difference in terms of "equivalent" core clock speed
of a couple hundred megahertz. (So, if a Pentium and a Celeron
run at the same core clock, it will be like the Pentium is a
couple hundred megahertz faster than the Celeron.)
Pentium processors also have the arbitration logic pinned out
to allow multiple processors. Pentiums are typically used
in duals (presumably their cache is too small for quads).
The Xeon is at the top of the heap, in terms of cache. One of
the reasons for this, is the Xeon tends to be a step behind
when it comes to the front side bus (FSB) clock rate. The
Xeon is normally only used in multiprocessor systems
(2, 4, 8) and the shared bus becomes very long to connect
multiple processors. The longer the bus, the lower the clock
speed allowed. To compensate for the "bus starvation" of the
processors, from sharing the same memory subsystem, extremely
large caches are used to reduce the percentage of the time
that the processor has to go out to the memory subsystem.
When selecting a processor from this lot, care must be taken,
as some processor types may not be properly supported in the
BIOS. Even if a Xeon could be plugged into a P2B, I don't know
how the BIOS would interpret that. For some of the Coppermine
(0.18 micron) and Tualatin (0.13 micron) processors, you'll
need a recent BIOS to have them properly recognized. In some
cases, a microcode patch is needed to make the BIOS "nag" free.
Just for fun, here is Intel's listing of what they current sell.
This will give you some idea of how many different models/types
of processors they make, many of which are irrelevant to the
desktop hobbyist.
http://www.intel.com/intel/finance/pricelist/
To look up the characteristics of Intel processors, try
http://processorfinder.intel.com
HTH,
Paul
