home *** CD-ROM | disk | FTP | other *** search
- Path: sparky!uunet!munnari.oz.au!mips!mips!darwin.sura.net!Sirius.dfn.de!math.fu-berlin.de!uniol!hb.maus.de!ms.maus.de!Sandor_Scari
- From: Sandor_Scari@ms.maus.de (Sandor Scari)
- Newsgroups: comp.sys.m68k
- Subject: Re: Zero-suppressed register?
- Message-ID: <A46550@MS.maus.de>
- Date: Tue, 25 Aug 92 22:30:00 GMT
- References: <A47192@HB.maus.de>
- Organization: MausNet
- Lines: 12
- X-Gateway: MausGate/News 1.11
-
- t> I do a little bit of 680xx programming for the Macintosh, and
- t>have occassionally seen mention of a "zero supressed register",
- t>denoted by e.g., ZA0. I couldn't find any mention of such an animal
- t>in the Motorola User's Guides, and am curious what it is. Is it
- t>something to do with the MMU and/or specific to a particular OS?
-
- No, its not an MMU or OS Feature. Its is hardware (or microcode) of the CPU.
- The "Z" is the assembler notation of the "IS"-bit (Index Suppress) of the Full
- Format Extension Word(s) on CPUs >= 68020.
-
- The suppressed register is NOT added in the address calcualtion.
- S\'andor
-