RE: formula for adjusting pci clock?

["Ingraham, Andrew" <Andrew.Ingraham@compaq.com>]

> Suppose I have a 66MHz mboard with 7 slots.  Obviously this is more 66MHz
> loads than is allowed, but is it possible to drive all 7
> loads if I slow down the clock?  If so, how much would I have to slow it
> down?  Is there some magic formula or "rule of thumb" out
> there that can tell me?
 
There is no known formula.  Also I would expect a very nonlinear function
between number of slots and clock speed, probably with big discontinuities.
(Adding one more slot might not change the maximum clock speed, but two more
might cut it in half, for example.)

Each case needs to be figured out, through simulations and/or lab
measurements, by the motherboard designer.

If it is a single PCI bus with 7 slots, it is possible that the clock might
need to be reduced to 25MHz to work reliably, but miracles are possible.

If you need 66MHz throughput, it might be better anyway to use multiple PCI
buses with fewer slots per bus.

Regards,
Andy