Xref: utzoo comp.sys.mac:21475 comp.unix.aux:443 Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!gatech!mcdchg!michael From: michael@mcdchg.chi.il.us (Michael Bodine) Newsgroups: comp.sys.mac,comp.unix.aux Subject: Re: Can an 030 need a PMMU? Message-ID: <13205@mcdchg.chi.il.us> Date: 13 Oct 88 19:24:14 GMT References: <10395@dartvax.Dartmouth.EDU> Reply-To: michael@mcdchg.chi.il.us (Michael Bodine) Organization: Motorola Microcomputer, Schaumburg, IL Lines: 26 Jeffrey Buchsbaum (63848e@eleazar.dartmouth.edu) writes: > I called Dove Computer today to ask about an '030 board ugrade for the II. They > ... > from a marketing point of view. I thought the 030 had the PMMU in it. > > One confused MacII hacker. Somebody's confused alright, but it wouldn't appear to be you! The 030 does have the mmu on-chip. The only way an 030 upgrade would still require an 851 for external memory management is if 1) their software disabled the on-chip mmu and 2) their (or somebody's) software required the full functionality of the 851 -- the 030 mmu is a subset of the 68851; not all instructions supported by an 020/851 pair are supported by the 030. Even so, there would have to be hardware modifications and code changes to support the fact that the off-chip mmu by default only responds to a particular co-processor id (i forget which, not relevant) so that any co-processor functions embedded in object code would operate with the on-chip mmu. To access an off-chip mmu, you'd have to recode all mmu instructions to reference a different co-processor id. Seems like an awful lot of hassle to go thru when not doing anything would most likely just make it work! Anybody in Austin listening? At Dove? -- [ Michael Bodine, michael@mcdchg.UUCP, (312) 576-7840 ] [ Opinions expressed are mine! All mine! ] [ Motorola couldn't have them even if they wanted them! ] [ No one else agrees with me; why should my employer? ]