Rene Herman wrote:
> On 22-02-08 09:12, Peter Teoh wrote:
>
>> This timing of 8Mhz (or 8.33Mhz right?)
>
> It's generally implemented as something like 7.5 to 8.33 yes, with that 8.33 
> being a specification figure.
>
>> is supposed to be 1/4 of the PCI bus speed of 33Mhz right?   (read from
>> altera website).
>
> No. It _can_ be divided down from the PCI clock but only if it'll do. It's 
> supposed to be at around 8 MHz, whetever the source.
>
Ok, I think I got what u meant.   I was confused by this device:

http://www.altera.com/products/ip/iup/pci/m-eur-pci-to-isa.html

I forgotten that ISA is a legacy feature, and this device is actually
trying to provide compatible function to map the PCI signal to ISA
function.

>> And so how about 66Mhz PCI bus - so for 8 bus cycles it will be half
>> of 1us, correct?
>
> No, although PCI-X system with an ISA bridge no doubt exist, any system 
> driving an ISA bus at 16 MHz would serve mostly as an ISA peripheral cooker.
>
> Rene.
>

Sorry, the above arises from my confusion of this altera's feature
against the standard, which of course does not link ISA to PCI speed.
 Thanks.

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