Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!think!bloom-beacon!mit-eddie!bbn!rochester!cornell!batcomputer!itsgw!steinmetz!uunet!portal!cup.portal.com!thad From: thad@cup.portal.com Newsgroups: comp.sys.amiga.tech Subject: Re: 020 and 32 bit memory Message-ID: <6756@cup.portal.com> Date: 22 Jun 88 08:25:00 GMT References: <6339@well.UUCP> Organization: The Portal System (TM) Lines: 18 XPortal-User-Id: 1.1001.2826 Yes, there is a good reason why a program will work on an '020 Amiga, then fail on a system with an '020 and 32-bit-wide memory (look to True Basic as one example of such failure). The reason: some crap software is using the high byte of a 32-bit pointer for some purpose OTHER than as part of the address (e.g. someone is sticking DATA into bits 31:24). On an Amiga withOUT the 32-bit-wide memory, the crap in bits 31:24 is simply not seen (or, at least, is ignored) by a memory address decoder. An Amiga WITH 32-bit-wide memory has that memory in the address space ABOVE the reach of 2^24, and the extra junk WILL be decoded to a non-existent address. Rephrased: on a system with 32-bit-wide memory, EVERY bit in an address pointer is considered to be part of an address; on a "standard" Amiga, only the information in bits 23:0 are considered part of an address.