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From: rhyde@koufax.ucr.edu (randy hyde)
Newsgroups: comp.sys.apple2
Subject: Re: MMu on the IIgs (COP v. BRK)
Message-ID: <11204@ucrmath.ucr.edu>
Date: 16 Jan 91 17:36:21 GMT
References: <278d0eda.563e@petunia.CalPoly.EDU> <91015.000214AABENSON@MTUS5.BITNET>
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Reply-To: rhyde@koufax.ucr.edu (randy hyde)
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>> On the II gs BRK has an operand.

This is an artifact of the disassembler.  The "operand" for the
break instruction goes all the way back to the 6502.  The original
chip had a bug which pushed the return address of the *next* instruction
(rather than next instruction minus one).  BRK handlers on the older
chips always compensated for this.  The GS' disassembler simply treated
BRK as a single byte instruction.  If you look at all manufacturer's 
literature, BRK is always listed as a single byte instruction.  It was
Apple who decided it should be a two-byte instruction.  COP, OTOH, is
listed in WDC's literature as a two-byte instruction.