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From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: net.micro.mac
Subject: Re: Re: Multitasking Considered Useless?
Message-ID: <1036@hoptoad.uucp>
Date: Mon, 25-Aug-86 04:50:29 EDT
Article-I.D.: hoptoad.1036
Posted: Mon Aug 25 04:50:29 1986
Date-Received: Mon, 25-Aug-86 19:31:26 EDT
References: <3150@ism780c.UUCP> <617@cbmvax.cbmvax.cbm.UUCP> <3218@ism780c.UUCP>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Centram Systems, Berkeley
Lines: 28

I'm currently working on UNIX-style multitasking software for the Mac
(experimentally).  Naturally, the biggest problem with multitasking, whether
Switcher, Servant, or mine, is the lack of memory management hardware in the
Macintosh.  I was thinking about putting together a memory-management add-on
board which would run a simple dual-processor multitasking Mac OS (using the
68000 as a hardware controller, and a 68010 at 10 MHz with no bus
arbitration for user-mode software).  I was going to use a 10 MHz 68451 chip
or two for the memory management, but it turns out that this takes 200 ns to
translate a logical address to a physical one.  This is clearly not
acceptable performance.  Anyone know of good memory management chips that
would be reasonably compatible with Motorola hardware?  (I know, I know:
"Why don't you burn your own logic arrays?")

This project would be a spare-time thing for my own fun, but if it worked
out particularly well I would consider licensing or selling the board.

Incidentally, the Mac Programmers' Workshop contains strong hints that the
forthcoming new Mac will contain a Motorola 68851 Paged Memory Management
Unit chip.  This chip is scheduled to be released last quarter this year or
first quarter next; Apple obviously has obtained some advance copies and
played with them, at the least.  I'd like to do the same, obviously, but
there are a few little availability problems....
-- 
Tim Maroney, Electronic Village Idiot
{ihnp4,sun,well,ptsfa,lll-crg,frog}!hoptoad!tim (uucp)
hoptoad!tim@lll-crg (arpa)

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