keith@Apple.COM (Keith Rollin) (10/23/89)
In article <871@cf-cm.UUCP> ralph@computing-maths.cardiff.ac.uk (Ralph Martin) writes: >MABuild has flags -needs68030 and -needs68020. I know the 68020 has extra >instructions compared to the 68000, but didnt realise this was also true of >the 68030 with respect to the 68020. What exactly are these differences? > >(one thing that worries me is that now the MacII is dead (oops, no longer sold) >programmers will be tempted to use -needs68030 and ignore poor MacII owners). I'm not exactly sure why there are both -needs68030 and -needs68020 flags for MABuild, considering that the two chips are very similar. As far as I know, the only significant changes are the built-in PMMU and larger on chip caches. This is born out by the fact that the MacApp library doesn't take advantage of any differences between the two chips. There are only two places where MacApp checks for a specific processor, and in both cases, it treats the 68020 and 68030 identically. An internal version of MacApp once had both -needsMC68881 and -needsMC68882 flags, but these were combined into the -needsFPU flag that is in 2.0b9. Considering that the difference between the 68020 & 68030 are about the same as the difference between the 68881 & 68882, I don't see why one set of flags got combined, and the other didn't. Also, where did you hear that the Mac II is no longer sold? I'm not aware that we've stopped selling it. Is this just a rumor, or did you read this somewhere (and I DON'T mean in "Mac the Knife")? The bottom line of all this is that I don't think that developers will suddenly refuse to write for the 68020. There is no percentage in it. About 99% still support the 68000, besides. -- ------------------------------------------------------------------------------ Keith Rollin --- Apple Computer, Inc. --- Developer Technical Support INTERNET: keith@apple.com UUCP: {decwrl, hoptoad, nsc, sun, amdahl}!apple!keith "Argue for your Apple, and sure enough, it's yours" - Keith Rollin, Contusions
ralph@computing-maths.cardiff.ac.uk (Ralph Martin) (10/23/89)
MABuild has flags -needs68030 and -needs68020. I know the 68020 has extra instructions compared to the 68000, but didnt realise this was also true of the 68030 with respect to the 68020. What exactly are these differences? (one thing that worries me is that now the MacII is dead (oops, no longer sold) programmers will be tempted to use -needs68030 and ignore poor MacII owners). Ralph
rcfische@polyslo.CalPoly.EDU (Raymond C. Fischer) (10/24/89)
In article <872@cf-cm.UUCP> ralph@computing-maths.cardiff.ac.uk (Ralph Martin) writes: >MABuild has flags -needs68030 and -needs68020. I know the 68020 has extra >instructions compared to the 68000, but didnt realise this was also true of >the 68030 with respect to the 68020. What exactly are these differences? Following is what I hope will be the definitive net answer to the question "What is the difference between the 68020 and 68030". What the 68030 has that the 68020 doesn't An on-chip mmu Additional control registers CRP, SRP, TC, TT0, TT1, MMUSR (all of which pertain to the MMU) New instructions: PFLUSH PLOAD PMOVE PTEST There are additional fields in the cache control register (CACR) to control the on-chip data cache. What the 68020 has that the 68030 doesn't: Two instructions: CALLM RTM Of course, there are hardware differences as well, but from the programming standpoint, this is it. My reference is the ... "MC68030 Enhanced 32-Bit Microprocessor User's Manual" by Motorola Ray Fischer rcfische@polyslo.calpoly.edu