[Tfug] Intel CPU compatibility

[Ronald Sutherland]

On Tue, Jun 3, 2008 at 11:10 AM, Bexley Hall <bexley401 at yahoo.com> wrote:

> Hi,
>
> I want to upgrade the processors in my SGI VWS.
> IIRC, it is currently configured as 1x450 (or maybe
> 2x450?).
>
> But, I don't know what all of the criteria are for
> "CPU swap"  :<
>
> Obviously, CPUs need to be in compatible packages
> (these are  :> ).
>
> And, FSB must be same speed.
>
> And, for pairs of CPUs, they need to be same stepping.
>
> But, are there other more subtle issues?  E.g.,
> does the VRM "auto-sense" the CPU and adjust Vout
> accordingly?  Or, do you have to fit the correct
> flavor VRM to the processor?
>
> The replacement processors (P3's) are labeled
> "800/256/100/165V".  I assume these to probably
> indicate CPU speed, onboard cache, FSB speed and
> VRM voltage"?
>
> If so, the first two values should be able to vary
> wrt my old CPUs (i.e., old CPU will undoubtedly be
> slower, possibly have a different amount of cache).
> The third value must agree (i.e., a 100 FSB wouldn't
> work *reliably* in a 133 FSB system -- and, I don't
> think you can *authoritatively* claim that a 133FSB
> CPU would work in a 100FSB system since so many
> of these things now have PLL's onboard and you
> can't be sure how wide the capture range is...)
>
> So, is the last value "for informational purposes"
> or must it agree with the corresponding value in the
> existing system?  (I'll have to pull the case off and
> see what the current markings are)
>
> Thanks for any help clarifying the alphabet soup!
> --don
>

On all my computers the CPU is the fastest part in the system they are well
over 10x the data bandwidth of most anything else (i.e. CPU to cache
bandwidth is huge). If I put a CPU that runs 10 times faster in those
computers, it will then run 100x faster than the rest of the system, and I
will add not much more than 9% increase to the bottom line performance
(except the programs that can run only in cache).
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