[comp.sys.mac] Indivisible R-M-W cycles on the Mac ][

dillon@CORY.BERKELEY.EDU (Matt Dillon) (03/23/88)

>IMV-5 warns against the use of the 68K TAS instruction saying that the
>read-modify-write memory cycle is not supported by the Mac ][ and SE
>hardware. Does anyone out there know why and to what extent this is true?

	Probably the same reason you can't do it on the Amiga ... it mucks
with the custom support hardware's timing.

>I am bothered by this since indivisible RMW cycles are important to the
>implementation of multi-processor/task architectures.

	Not as important as you think, though definately convenient.

					-Matt