Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site sftig.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!mhuxm!sftig!rbt
From: rbt@sftig.UUCP (R.Thomas)
Newsgroups: net.micro.apple,net.micro.68k
Subject: Re: 68000 vs 6502 (!)
Message-ID: <596@sftig.UUCP>
Date: Wed, 2-Oct-85 13:55:05 EDT
Article-I.D.: sftig.596
Posted: Wed Oct  2 13:55:05 1985
Date-Received: Thu, 3-Oct-85 07:03:28 EDT
References: <151@uvicctr.UUCP> <7100003@prism.UUCP>
Organization: AT&T Bell Laboratories, Summit, NJ
Lines: 46
Xref: watmath net.micro.apple:2192 net.micro.68k:1184

> 
> 
> 
> 
> 	Why not drop in 65802's to replace your 6502's?
> 
> 	The 65802 is the 6502 pin-compatible version of the
> 	65816, the new 16-bit 6502.  The 65816 features 16 
> 	megabyte adressing, user registers that can be expanded
> 	from eight bits to sixteen, a sixteen-bit stack pointer,
> 	a relocatable zero page (now called the direct page), a block
> 	move instruction, and much more.  In its emulation mode,
> 	it emulates a 6502 down to the weird invalid addresses
> 	needed to operate the Apple disk II controller; in native
> 	mode, you already know over half the opcodes if you know how to
> 	program a 6502.
> 
> 	If a 1MHz 6502 can keep up with an 8MHz 68000, what will happen
> 	when somebody builds a machine using a 4 or 5 MHz 65816 --
> 	which will be exactly four or five times faster, since the
> 	memory access cycle is the same as the clock cycle?  (The
> 	standard 65802/65816 part is 4MHz, and it's CMOS).
> 
> 	For more information, contact the Western Design Center, 2166
> 	East Brown Road, Mesa, AZ, 602-962-4545 (it is also being
> 	sourced by GTE Microcircuits).
> 
> 		David Eyes
> 		Mirror Systems, Inc.
> 
> 		{cca, ihnp4, inmet, mit-eddie, wjh12} ...
> 				... mirror!prism!david

Does anybody know whether you can replace the 65(C)02 in an Apple IIe/+/c with
the 65802 without causing serious compatibility problems?  If you do, and if
it works, what do you get for your efforts?  No chance of direct
addressability to memory beyond the II's hacked over 64K, of course, but do
the 16 bit registers work?, howabout the 'direct' page stuff?, the block move
instructions?  Does it mess up any of the timing loops (like in the disk driver
software, and the paddle reader software)?  Or did they preserve the same
number of clocks per instruction as the 6502 as a compatibility 'feature'?

Interesting,

RIck Thomas
ihnp4!attunix!rbt