Path: utzoo!attcan!uunet!husc6!think!ames!ncar!tank!uxc!uxc.cso.uiuc.edu!a.cs.uiuc.edu!p.cs.uiuc.edu!gillies
From: gillies@p.cs.uiuc.edu
Newsgroups: comp.sys.mac
Subject: Re: Advantages of a 68030 and a IIx
Message-ID: <76000295@p.cs.uiuc.edu>
Date: 5 Oct 88 16:50:00 GMT
References: <578@bruce.oz>
Lines: 21
Nf-ID: #R:bruce.oz:578:p.cs.uiuc.edu:76000295:000:833
Nf-From: p.cs.uiuc.edu!gillies    Oct  5 11:50:00 1988


Maybe the 68030 in the Mac IIx benefits APPLE, not the customer

- Perhaps Apple wanted to get a jump on Sun & NeXT, so they could claim
  "We have a 68030 machine".

- The Apple MMU & Socket cost $$$ in manufacturing (there is a stub
  MMU in a regular Mac II without the 68851) -- this money can be
  saved in a 68030 machine.

- There is only 1 configuration of IIx system board (no sockets), so
  board swaps are simpler, inventory is simplified (no 68851's to stock).

Or, maybe it benefits A/UX customers

- Is it true that 68030 $$$ <= 68020 $$$ + 68851 $$$  ?

- The 68851 is a SLOW paging chip -- it adds 1 wait-state to A/UX memory
  references.  Sun/etc. get around this with their own PMMU designs.  Does
  the 68030 have this wait state?  If not, then putting the 68030 in
  the IIx speeds up A/UX (but not the Mac O/S).