66 MHz Capability bit in AGP

[havard@brooktree.com (havard scott)]

I am facing a dilemma in how to set the PCI Config Register 66 MHz
capability bit for an AGP compliant device. We plan to be compliant
with the 66 MHz timing requirements of the AGP bus, but not the
more stringent 66 MHz timing requirements of the proper PCI bus. Also, 
we intend for our chip be able to go on a PCI-33 board as well as an AGP 
board.

This raises the question of how to set the 66 MHz capable bit. On the 
one hand, it seems that we should set it to zero so that one could plug
our part into the PCI bus, without incorrectly indicating that
it is capable of 66 MHz operation. As for the case where it was on the AGP
bus, the AGP will always run at a minimum of 66MHz, so it doesn't seem it 
would matter whether our 66 MHz bit was set or not.

On the other hand, I'm worried about a system BIOS that will 
have a problem with an AGP device that doesn't have it's 66 MHz
bit set. It might decide to not enable our card. Also, for the 
case when our device is on the true PCI bus, I'm not
sure if it matters that we incorrectly indicate we are 66 MHz 
capable in that environment. I am underthe impression that no system
vendors are currently moving to implement a 66 MHz PCI bus.

I'd appreciate any feedback.
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