Re: sym53c875E-0: PCI clock seems too high

Paul Flinders (paul@dawa.demon.co.uk)
26 Sep 1999 16:19:43 +0100


Andreas Bombe <andreas.bombe@munich.netsurf.de> writes:

> On Sat, Sep 25, 1999 at 11:08:26PM +0200, Gerard Roudier wrote:
> > Overcloking a CPU that is in fact sold with an underclocked specification
> > is one thing. Overclocking a BUS and then everything that connect to it by
> > more than 10% was not imaginable by me. By the way, I think that people
> > that overclock PCI 33 Mhz buses up to 41MHz or more are just foolish and
> > plain idiot, but I don't care of them.
>
> Even though bus overclocking may work for many devices, SCSI
> controllers are known to react very allergic to that. Overclocking the
> bus while using SCSI is therefore exceptionally stupid, given that data
> integrity could suffer.

First off let's remember how CPU's are manufactured. Typically there's
no difference between, say, a 433Mhz chip and a 333Mhz chip - the
likelyhood is that they came off the same production line and the only
difference is that the faster chip passed a (quite short) set of tests
at that speed.

The same applies to all the components in the system - all are
designed to work with an "acceptable" error rate at a given speed but
some will work at higher speeed, however, unlike CPUs there's not
usually a higher value attached to faster parts.

I don't really see that there's any fundamental difference between
overclocking a bus and overclocking a CPU - both are making an
assumption and a trade-off between the acceptable safety margin and
performance. For my home machine this trade off definately favours
performance.

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