At 15:29 Uhr -0700 13.3.2007, Jason Thorpe wrote:
>Ok, so, sounds like it's not an issue on m68k -- CAS can be used on
>all Amiga hardware that NetBSD supports.

Apple's HW-520 technote
http://developer.apple.com/technotes/hw/pdf/hw_520.pdf has this to say:

"Macintosh II CPUs perform an Attention-Resource Lock cycle as a prelude to
Read-Modify-Write cycles to NuBus addresses. There is no other way to
initiate bus or resource locking from the Macintosh CPU. Macintosh CPUs do
not support locking NuBus for longer tenures. The only Read-Modify-Write
instructions are TAS, CAS, and CAS2.

Use of these instructions is problematic, as they may introduce timing
problems for certain CPUs (see the Macintosh Technical Note "Macintosh
IIfx: The Inside Story"), and the operand address must always be previously
cached in the MMU
address translation cache or else a bus error results. They must be used
with extreme care."

FYI,
	hauke

--
"It's never straight up and down"     (DEVO)