Path: utzoo!attcan!uunet!pdn!alan From: alan@pdn.UUCP (Alan Lovejoy) Newsgroups: comp.sys.m68k Subject: Re: 68020 in a *68010* socket? Message-ID: <3373@pdn.UUCP> Date: 6 Jun 88 14:15:21 GMT References: <17206@gatech.edu> <10123@mcdchg.UUCP> <17479@glacier.STANFORD.EDU> Reply-To: alan@pdn.UUCP (0000-Alan Lovejoy) Organization: Paradyne Corporation, Largo, Florida Lines: 28 In article <17479@glacier.STANFORD.EDU> jbn@glacier.UUCP (John B. Nagle) writes: >I'd like to suggest to Motorola that they bring out a 68020 in a >form pin-compatible with the 68010 and 68000. The object is software >compability; it's annoying that one can't run the same software on all >machines of, say, the Apple line. This causes trouble in the retail software Pin compatibility has nothing whatever to do with software compatibility. The software incompatibiliites between the '000, the '010 and the '020 are caused by the fact that some instructions do not have the same privilege status on the '010 and '020 as they do on the '000 (which should normally only affect operating system code), by the fact that the '020 has an instruction cache which invalidates some "dirty tricks" involving self-modifying code which Motorola warned everyone would not be portable and by the fact that the chips may operate at different clock speeds and execute instructions in a different number of cycles, causing problems for code which tries to mark time by executing a known number of instructions with a known number of cycles. Pin compatibility means that two different chips can be plugged into the same socket and both will work--it does not mean that both chips are necessarily software compatible in any way! -- Alan Lovejoy; alan@pdn; 813-530-8241; Paradyne Corporation: Largo, Florida. Disclaimer: Do not confuse my views with the official views of Paradyne Corporation (regardless of how confusing those views may be). Motto: Never put off to run-time what you can do at compile-time!