On 19 Apr 99, at 8:05, Charles M Yates wrote:

>    I'm not sure if this is off-topic or not, but here goes. Recently, my
> power supply died and took my hard drive, motherboard, etc. with it. I
> had a major rebuild done using the cyrix 6x86 mk II cpu. The shop was
> supposed to use a 300 mhz cpu, but my display says it is a 233 mhz cpu.
>    When I called the shop about this, they tried to tell me they used a
> 233 mhz cpu because it was as fast as a pentium 300 mhz chip. Personally,
> I think this is hogwash, but first I'd like to find out if the 233 mhz
> cyrix cpu is as fast as a 300 mhz pentium chip.
>    Secondly, I would like to ask for suggestions about how to handle
> these people and this situation. They did list the cpu as a 300 mhz cyrix
> 6x86 M II chip (no other description), so I definitely feel they are
> practicing deceptive advertising at the least. TIA

  Cyrix's CPU design is not simply a copy of Intel's Pentium; it's a complete
redesign to execute the same software.  One of the results is that the same
set of instructions can, on the two different designs, take a very different
number of "clock cycles" to complete.
  WHile there are exceptions, in general most operations will complete a bit
faster on the Cyrix than on the Pentium.  AT, say 166 MHz, the Cyrix will get
more done than a Pentium would.

  CYrix and AMD came up with a way to try and use this in their marketing --
the "PR rating" system.  So instead of matching the 166 MHz Cyrix against the
slower Pentium 166, the Cyrix running at 133 MHz was designated "PR166"
because it would, on some application loads, complete work a little faster
than a 166 MHz Pentium.  The PR rating attempts to provide performance
comparison, but does not measure actual clock frequency.

  AMD no longer uses the PR system in their marketing, but Cyrix does.
You'll have to look very closely at your purchase documents!  If they say
"300 MHz CPU", then you have a legitimate beef.  If they say "Cyrix MII-300"
or "PR300", those may very well refer to a CPU model that really runs at the
233 MHz that your BIOS reports, and they have delivered exactly what was
called for.

  [You will undoubtedly hear from some people that there is something "wrong"
with the Cyrix CPUs.  They will probably be referring to one of three things:

1. Some software installers (notably from Creative Labs for some sound card
utilities) note recognize a Cyrix CPU as a "Pentium or better".  I had the
same code fail to recognize a dual PII-266 system, so I consider this a
software bug.

2. Win95 and NT each had issues with recognizing and properly using some 6x86
(M1) chips.  These are all supposed to be fixed in the MII.

3. Intel's patented pipelining of the FPU (floating-point unit) means that
applications that depend heavily on this feature run poorly on non-Intel
CPUs.  There are several 3D games that fall into this category.

  On the flip side, not only does the CYrix execute most common instructions
faster than the Pentium, it also handles the CPU load associated with
IDE/EIDE much better, giving it excellent bang-per-buck in typical business
and desktop applications.  It may or may not be a good choice for any given
machine.]


David G

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