Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!bcm!lib!thesis1.hsch.utexas.edu From: jmaynard@thesis1.hsch.utexas.edu (Jay Maynard) Newsgroups: comp.arch Subject: Re: The CPU with 3 brains---486 compatibility with 8008 Message-ID: <4326@lib.tmc.edu> Date: 16 Nov 90 10:58:30 GMT References: <1990Nov6.223738.13265@ux1.cso.uiuc.edu> <9333@b11.ingr.com> Sender: usenet@lib.tmc.edu Organization: University of Texas Medical School at Houston Lines: 20 Nntp-Posting-Host: thesis1.hsch.utexas.edu In article em@dce.ie (Eamonn McManus) writes: >lhughes@b11.ingr.com (Lawrence Hughes) writes: >I would not be surprised to discover that there are no programs in existence >that are affected by this change (unless they use it deliberately to see >which processor they are running on). About the only arithmetic >instruction where you would be interested in the resulting parity is (in >Z80-speak) `adc a,a' which rotates left the accumulator and carry. There was one case. The first couple of versions of Altair BASIC, developed for the MITS Altair 8800 by Bill Gates and later to become Microsoft BASIC, was affected by this change, and had to be patched to run on a Z-80. Interestingly enough, Gates could not officially release the patches, since his contract with MITS specified that the interpreter was only to be sold for Altair systems, and no Altair system ran a Z-80 (at least as far as MITS was concerned). I don't know the instruction sequence they used that tickled the problem. -- Jay Maynard, EMT-P, K5ZC, PP-ASEL | Never ascribe to malice that which can jmaynard@thesis1.hsch.utexas.edu | adequately be explained by stupidity. "With design like this, who needs bugs?" - Boyd Roberts