Re: sym53c875E-0: PCI clock seems too high

Peter Desnoyers (pjd@fred001.dynip.com)
Thu, 30 Sep 1999 06:23:13 -0400 (EDT)


Andreas Bombe wrote:
>
> However, according to c't (which did overclocking tests on PCI), SCSI
> controllers can almost be expected to fail. Probably because they
> drive some internal clock from PCI or the chips are clocked from PCI
> and, unlike CPUs, are built only for 33MHz. SCSI controllers are
> apparently coupled to the bus clock tighter than other devices.

Hopefully it's for a different reason than that, as deriving a clock
from the PCI bus is an explicit violation of the bus spec. (think about
what happens when you underclock the bus, which is quite legal; changing
the clock in midstream and other things hostile to PLLs are also legal,
I believe.)

My own two cents on the issue - I've got an old socket 7 motherboard that
overclocks the PCI bus for higher FSB speeds, and the first time I did
that it ate my tulip card. That'll teach me...

-- 
............................................................................
 Peter Desnoyers 
 162 Pleasant St.         (617) 661-1979          pjd@fred.cambridge.ma.us
 Cambridge, Mass. 02139   (978) 461-0402 (work)   pjd@giga-net.com 

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