On Mon, 14 Jan 2002, David A. Gatwood wrote:

> It's pretty similar to PCI.  The only thing it had in common with the
> nubus machines, at least from a programming perspective, was the existence
> of nubus itself, which is supported through a BART bridge chip so that it
> is relatively isolated from the CPU bus.

Technically, I'm not being fair.  There are a number of chips on the PDM
family motherboards that are used on AV Quadras.  Those chips are also
(almost?) all used on the early PCI PowerMacs, however.  :-)


> Interrupt handling is like PCI, in that all interrupts except for those
> from actual nubus cards can be acked in the code for the interrupt
> controller itself (nubus cards being constrained by compatibility with
> existing cards).  All the motherboard chips are roughly the same as the
> 7x00 PCI machines (Cuda, MACE, 53C94 SCSI, AWACS).

Except for video, DMA, and 53CF94 (fast internal SCSI, 8100 only).
However, none of these are strictly necessary to bring the system to a
usable state.  (Video helps, but even if you just get the address and bit
depth right, you have enough for a basic B&W console without even writing 
any further driver code.)


Later,
David

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