John_Miller@mindlink.UUCP (John Miller) (03/30/91)
In article <7720@idunno.Princeton.EDU>, bskendig@bonnet.Princeton.EDU (Brian S. Kendig) writes > Apple once told developers that they could safely assume any > 020- or 030-based Macintosh would have a math coprocessor > in it. Apparently they warned people about their change in policy > while they were designing the LC and IIsi, but by then people > were already using applications which assumed the coprocessor. I have heard this before. Perhaps it is true. Lacking a close personal friend in Apple's DTS or engineering groups, I have always relied on Apple's Tech Notes to guide me through compatibility issues. Yes, there was the Compatibility Alert dated June 1990 that said "Listen, we are definitely going to have a 020/030 model without an FPU," but the warnings about FPU-checking date back to 1987. Tech Note #129, first released in May, 1987, documented the SysEnvirons call which included a field to indicate whether an FPU was present. When an FPU check was so easily available, I fail to understand why a programmer would decide to do a "once removed" test on the main CPU type. There is a gap in my Tech Notes but it appears that by October 1988, Tech Note #129 had been modified to include the more explicit warning: "Regardless of the version used, however, your software should be prepared to handle unexpected values and should not make assumptions about functionality based on current expectations. For example, if your software currently requires a Macintosh II, testing for machineType >= envMacII may result in your software trying to run on a machine which does not support the features it requires, so test for specific functionality (i.e., hasFPU, hasColorQD, etc.)." Tech Note #236, "Speedy the Math Coprocessor", was released in June 1989. It starts by repeating that SysEnvirons should be used to detect an FPU. I suspect that many of the applications that had problems with the LC/si would have received at least minor updates between June 1989 and the LC/si release. Apple is not without sin in the compatibilty game, but I think they have handled the FPU properly. As long as there has been an FPU Mac, there's been an easy and safe way of checking for the presence of an FPU. ______________________________________________________________________ John Miller (604) 433-1795 Symplex Systems AppleLink (rarely) CDA0461 Burnaby, British Columbia Fax: (604) 430-8516 Canada usenet: john_miller@mindlink.uucp Macintosh Consulting and Software Development ______________________________________________________________________