Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!n8emr!cmhgate!f200.n226.z1.FIDONET.ORG!Adam.Frix From: Adam.Frix@f200.n226.z1.FIDONET.ORG (Adam Frix) Newsgroups: comp.sys.mac.hardware Subject: Re: PMMU question Message-ID: <27044.2543231E@cmhgate.FIDONET.ORG> Date: 23 Oct 89 01:01:47 GMT Sender: ufgate@cmhgate.FIDONET.ORG (newsout1.26) Organization: FidoNet node 1:226/200 - Aurora Borealis, Gahanna Oh Lines: 37 Nathan James Loofbourrow writes: >Brian Willoughby writes: >>Just a quick question. If the optional PMMU chip for the Mac II is >>NOT installed then how does the address bus get driven? I'm >>assuming that > >This question has an interesting answer (as opposed to all those >questions with really dumb answers ;-) )... There's a doohickey >known as the HMMU sitting in the PMMU slot of an pre-PMMU'd Mac II. >The HMMU apparently followed the previous designs, the GMMU and the >FMMU in reverse chronological order; thus its name, as the FMMU was >the "Fake Memory Management Unit". > >Ask for trivia, get trivia. That's how I found this info out. > >Nathan I recently flipped through a very new (1989) book about the Mac II (obviously written before the 030 machines came out, but published afterwards). It was allegedly a technical treatment of the machine, but I didn't look at it that closely. What I did read was that HMMU stood for "Hochsprung Memory Management Unit" or some such thing. Now, I know perfectly well that the Deep Shit Manager has been referred to a few other ways by people not in the know (Desperate Situation Manager, etc.), so I'll use this bandwidth to ask: was the author of this book just spouting off, because he didn't know any better? I mean, F,G,HMMU sounds so simple--and, of course, the simplest explanation is usually the correct one--that I'm questioning this Hochsprung MMU thing. --Adam-- -- Adam Frix via cmhGate - Net 226 fido<=>uucp gateway Col, OH UUCP: ...!osu-cis!n8emr!cmhgate!200!Adam.Frix INET: Adam.Frix@f200.n226.z1.FIDONET.ORG