Path: utzoo!attcan!uunet!seismo!esosun!ucsdhub!jack!elgar!ford From: ford@elgar.UUCP (Mike "Ford" Ditto) Newsgroups: comp.sys.m68k Subject: Re: 68020 in a *68010* socket? Summary: executing 68020-only instructions on old mac/atari/amiga/etc... Message-ID: <181@elgar.UUCP> Date: 11 Jun 88 06:51:03 GMT References: <17206@gatech.edu> <10123@mcdchg.UUCP> <17479@glacier.STANFORD.EDU> <6276@cup.portal.com> <17482@glacier.STANFORD.EDU> Reply-To: ford@kenobi.UUCP (Mike "Ford" Ditto) Organization: Omnicron Data Systems, Bonita, CA Lines: 44 In article <17482@glacier.STANFORD.EDU> jbn@glacier.UUCP (John B. Nagle) writes: >In article <6276@cup.portal.com> thad@cup.portal.com writes: >>Why do you feel there's such a software incompatibility between the various >>680x0 processors? >> > The problem is, of course, the multiply hardware. The floating-point instructions are far more significant, followed by the new addressing modes and the 32-bit instructions. > [ description of new, faster, better software that won't run on the > older CPU's ] ... > This history will repeat itself at the low end, on the Mac and Amiga >lines. As the mainstream products become 68020-based, more software will >be built that assumes a 68020 platform. This software will not run on the >smaller machines of the product line. > > What will be needed is a part that the manufacturers can use in later >versions of their low-end machines that handles the instruction set of the >68020 but is electrically compabible with the 68010. This part already exists, it's Motorola part number MC68010. A relatively simple change to the operating system is required to use it (if the O.S. was written for 68000-only), but then the full 68020 (and '030, and '040, ...) instruction sets can be executed by adding an emulation package. This software can be upgraded as Motorola adds new instructions to the 68000 family, and it will allow normal 68000 code to run at full speed. The emulated instructions will run slower than they would if done in microcode, but they will work. In other words, Motorola has done their part, now Apple, etc., can do their part... if they feel there is a need. At this time, I think it's best for Mac and Amiga software to be distributed in 68000- acceptable form since the 68000-to-68020 ratio is still pretty high. It will change, of course, especially now that Apple and CBM have 68020 and 030 products. -=] Ford [=- "Once there were parking lots, (In Real Life: Mike Ditto) now it's a peaceful oasis. ford%kenobi@crash.CTS.COM This was a Pizza Hut, ...!sdcsvax!crash!kenobi!ford now it's all covered with daisies." -- Talking Heads