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From: david@prism.UUCP
Newsgroups: net.micro.apple
Subject: Re: Orphaned Response
Message-ID: <7200006@prism.UUCP>
Date: Mon, 21-Oct-85 13:37:00 EDT
Article-I.D.: prism.7200006
Posted: Mon Oct 21 13:37:00 1985
Date-Received: Thu, 24-Oct-85 07:12:58 EDT
References: <2230@sdcc6.UUCP>
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Nf-ID: #R:sdcc6:-223000:prism:7200006:177600:1380
Nf-From: prism!david    Oct 21 13:37:00 1985





	No, the *65802* is pin-compatible with the 6502.  It
	achieves this by ignoring the bank address on its internal
	bus.  It is otherwise a 65816, and is
	always generating 24-bit addresses internally,
	but they are not propagated to the outside world on the
	65802.  In addition to not being 6502 compatible because
	the bank address is multiplexed over the data pins, the
	65816 also lacks some of the clock signals of the 6502, and
	includes several new signals (notably ABORT, Vector Pull
	(is an interrupt vector being addressed?), M/X (status of	
	m and x bits in status register), E (emulation or native mode),
	and VPA and VDA (valid program and valid data address).

	As to whether the 65802 will work in all apples, the answer
	seems to be: to the same extent as the 65C02 has worked in
	all apples, which is to say, all //e's and //c's, and some II's 
	and II+'s.  A recent issue of "Apple Assembly Lines" 
	has an analysis of this problem, which is due to timing differences,
	which can (apparently) been overcome by replacing some of the
	parts used in the timing signal generation.

	My own experience has been that 65802 has worked in both
	my //e and my II+, but then the 65C02 worked in my II+ also.



--		

David Eyes	{mit-eddie, ihnp4!inmet, wjh12, cca, datacube} !mirror!david
Mirror Systems	2067 Massachusetts Ave.
617-661-0777	Cambridge, MA, 02140