Path: utzoo!attcan!uunet!lll-winken!ames!pasteur!ucbvax!UIAMVS.BITNET!AWCTTYPA
From: AWCTTYPA@UIAMVS.BITNET ("David A. Lyons")
Newsgroups: comp.sys.apple
Subject: testing for 65C02 presence
Message-ID: <8901161831.aa18496@SMOKE.BRL.MIL>
Date: 17 Jan 89 01:49:45 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 38
X-Unparsable-Date: Monday 16 Jan 89 5:25 PM CT

>Date: Sun, 15 Jan 89 05:21:59 PST
>From: pbhyd!ldcol@pacbell.pacbell.com
>Subject: Re: testing all 3 parts of IIe enhancement

I wrote:
>Also from the monitor, type
>
>300:A9 00 1A 00
>300G
>
>You should get a register dump; I just need to know the value after
>"A=".  It should be 00 if you have a 6502 and 01 if you have a
>65C02.

Larry Colton asks:
>David, can you please explain why the above works?  What is the difference
>between the 6502 and the 65c02 as far as how the above code is treated?

On the 6502, opcode $1A doesn't do anything (anybody want to
guarantee that? as fasr as _I_ know it doesn't); on the 65C02, $1A
is "INC A" (or just "INC"), which adds one to the A register.

So the above program is

300:A9 00  LDA #$00
302:1A     INC
303:00     BRK

It loads A with zero, increments it to 1 _if_ a 65C02 (or 65802, or
65816, for that matter) is running the code, and then Breaks into
the monitor with a register dump.

>Larry Colton                {att,bellcore,sun,ames,pyramid}!pacbell!ldcol

--David A. Lyons              bitnet: awcttypa@uiamvs
  DAL Systems                 CompuServe:  72177,3233
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