brianw@microsoft.UUCP (Brian Willoughby) (10/18/89)
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
the page address bits from the 68020 are sent to input pins on the PMMU
and the PMMU generates the physical address value. Is there some plug
for the (ancient) Mac II which passes through the address bits?
The Terminally Curious,
Brian Willoughby
UUCP: ...!{tikal, sun, uunet, elwood}!microsoft!brianw
InterNet: microsoft!brianw@uunet.UU.NET
or: microsoft!brianw@Sun.COM
Bitnet brianw@microsoft.UUCPnl0s+@andrew.cmu.edu (Nathan James Loofbourrow) (10/19/89)
Brian Willoughby <brianw@microsoft.UUCP> 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
steve@violet.berkeley.edu (Steve Goldfield) (10/19/89)
In article <kZDC=2y00Uh_02gYA5@andrew.cmu.edu> nl0s+@andrew.cmu.edu (Nathan James Loofbourrow) writes: #>Brian Willoughby <brianw@microsoft.UUCP> 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 But you didn't answer the question. Somebody posted a very complete explanation about the PMMU, including a description of what the HMMU does, in comp.sys.mac a few weeks ago. He said that it does pass through the addresses, which is what the poster asked. The HMMU (this I know from taking it out and putting in a PMMU) looks like a plug with 50 or sixty pins. It seems to be called an 8737A V1475 (I got mine out and looked at it; it also says 3 4 3-0002-1, copyright Apple '86 on the back. To be complete, it says VLSI-70 on the pin side.). Steve Goldfield
bklaas@cmdfs2.intel.com (Brian Klaas~) (10/20/89)
In article <8092@microsoft.UUCP> brianw@microsoft.UUCP (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 >the page address bits from the 68020 are sent to input pins on the PMMU >and the PMMU generates the physical address value. Is there some plug >for the (ancient) Mac II which passes through the address bits? Apple included its own MMU. It does exactly that... Passes the address bits directly through. Owner of an Ancient Mac II, -- ** Brian Klaas, Design Engineer *** DISCLAIMER: All opinions ** ** Intel Corporation *** stated here are strictly my own. ** ** InterNET -> bklaas%cmdfs2.intel.com@relay.cs.NET UUCP: ** ** {hplabs,decwrl,oliveb,pur-ee,qantel,amdcad}!intelca!mipos3!sedona!bklaas **
Adam.Frix@f200.n226.z1.FIDONET.ORG (Adam Frix) (10/23/89)
Nathan James Loofbourrow writes: >Brian Willoughby <brianw@microsoft.UUCP> 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
wilkins@jarthur.Claremont.EDU (Mark Wilkins) (10/24/89)
In article <27044.2543231E@cmhgate.FIDONET.ORG> Adam.Frix@f200.n226.z1.FIDONET.ORG (Adam Frix) writes: >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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ It is not entirely clear that this is not the correct name for the thing. However, the technical staff at Apple have never seemed above a joke once in a while on a nonessential matter. The marketing folks have no such sense of humor, though. By the way, this is why the original Mac had 128K of RAM. -- Mark Wilkins wilkins@jarthur.claremont.edu
pkr@maddog.sgi.com (Phil Ronzone) (10/25/89)
In article <27044.2543231E@cmhgate.FIDONET.ORG> Adam.Frix@f200.n226.z1.FIDONET.ORG (Adam Frix) writes: >Nathan James Loofbourrow writes: > >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. The Mac II was designed by Mike Dhuey and Ron Hochsprung, and made to work by Ron Hochsprung. Ron did the simple idiot chip known as the HMMU, and yes, the H stood for Hochsprung. BTW - the HMMU does NOT simply pass the address lines through. It maps some addresses, and most importantly, chops off the high order byte so that the 24-bit idiot apps don't blow up. For a long while, we called the HMMU the "fake MMU". There was also an MMB, but that is another story ... ------------------------------------------------------------------------------- Phil Ronzone Manager Secure UNIX pkr@sgi.COM {decwrl,sun}!sgi!pkr Silicon Graphics, Inc. "I never vote, it only encourages 'em ..." -------------------------------------------------------------------------------
noah@Apple.COM (Noah Price) (10/25/89)
In article <27044.2543231E@cmhgate.FIDONET.ORG> Adam.Frix@f200.n226.z1.FIDONET.ORG (Adam Frix) writes: > >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. >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. In my copy of the Mac II Family Hardware Reference ('88), HMMU and Hochsprung Memory Management Unit don't appear in the text, but are cross-referenced in the index to AMU. The H did indeed come from Hochsprung, the name of one of the chip's designers. noah ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ noah@apple.com Mac IIci Hardware Design Team ..!{sun,decwrl}!apple!noah Apple Computer, Inc.
russotto@eng.umd.edu (Matthew T. Russotto) (10/25/89)
In article <35885@apple.Apple.COM> noah@Apple.COM (Noah Price) writes: >In my copy of the Mac II Family Hardware Reference ('88), HMMU and Hochsprung >Memory Management Unit don't appear in the text, but are cross-referenced in >the index to AMU. The H did indeed come from Hochsprung, the name of one of >the chip's designers. > Doesn't necessarily mean anything. Apple has an acronym for "LISA". And in one Apple document I found a reference in the index to WOM-- Write-Only Memory, where you put information but you can never ever get it out. It contained an X-Ref to a book by Bruce Tognazzi. Moral: Don't belive everthing Apple tells you. (So, anyone know if SWIM stands for Sanders-Wozniak Integrated machine or Super Wozniak Integrated Machine?) > >noah -- Matthew T. Russotto russotto@eng.umd.edu russotto@wam.umd.edu rrn: newsgroup "junk" full --- rerouting to news.groups
CXT105@PSUVM.BITNET (Christopher Tate) (10/26/89)
In article <1989Oct24.220445.707@eng.umd.edu>, russotto@eng.umd.edu (Matthew T. Russotto) says: > [...] And in one Apple document I found a reference in the index to WOM-- >Write-Only Memory, where you put information but you can never ever get >it out. It contained an X-Ref to a book by Bruce Tognazzi [...] This is certainly quite possible. If the memory addresses in question map directly to chip registers, then you may well not be able to read from them. An example of this was the old Commodore 64's (and possibly 128's) sound chip management registers. Reading the registers gave meaningless results. ------- Christopher Tate | somewhere i have never travelled, cxt105@psuvm.psu.edu | gladly beyond any experience, ..!psuvax1!psuvm.bitnet!cxt105 | your eyes have their silence.