Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!rutgers!uwvax!umn-d-ub!nic.MR.NET!shamash!raspail!bga
From: bga@raspail.UUCP (Bruce Albrecht)
Newsgroups: comp.sys.mac
Subject: Re: When will MacOS get virtual memory?
Message-ID: <962@raspail.UUCP>
Date: 10 Oct 88 18:33:15 GMT
References: <1526@oakhill.UUCP> <551@dms.UUCP> <8253@cit-vax.Caltech.Edu>
Organization: Control Data Corporation, Arden Hills, MN
Lines: 46

In article <8253@cit-vax.Caltech.Edu>, wetter@tybalt.caltech.edu (Pierce T. Wetter) writes:
>   Criticizing the 68000 for not having support for various "modern" features
> is like criticizing Newton for not knowing Quantum Physics. The 68000 made 
> small, powerful computers available to a lot of people. These people went on 
> to invent better ways to do things. OF COURSE THE 68000 doesn't support them
> they weren't invented yet. The 68000, by allowing you to address 16 Meg of
> memory was ahead of its time. Remember, people used to build MAINFRAMES with
> 64k of memory and 10 meg of disk space (and lots and lots of tape drives.)

Memory Management is not a "modern" feature.  It was around then.  Motorola
originally planned to support it on the 68000, and National did support it
on the 16032.  The real problem has always been to figure out how to put all
of that circuitry onto the space available.  Motorola and National certainly
planned on supporting a full 32 bit address space, but didn't have the room
on the first generation 16 bit processors.

In the 1960's, mainframes may have only had 64k memory, and 10 meg disk drives,
but by the late 1970's, most mainframes had 1 meg or more of memory, and 150+
meg drives, and only entry level minicomputers and mainframes were that small.

>    The state of the art is NOT the 68000 ANYMORE. Don't lambaste the 68000 for
> not having various features. It didn't need them. Now that microcomputers need
> more power, we have the 68020, 030 and the 88000 series. They're the future,
> not the 68000.

Even though the 68000 isn't state of the art, there's a lot of them being put
into newly manufactured machines (Mac+, Mac SE, etc.).  Market economics
prevent you from ignoring them when you develop products for only state of
the art computers that are mostly compatible with earlier generations of
the microprocessor family.

>   Of course, if you want to talk about brain-damaged microprocessors, what
> about the 68008. The 8-bit version of the 68000. 32/16 I can understand, but
> 32/8?

This isn't as stupid as you think.  The 68008 was meant to be used for
controlling devices on an 8-bit bus, not for general purpose computers.  By
using the 68008, designers got the speed of the 68000 (mostly), and the lower
cost of a 8 bit bus.  Of course, if you ever needed to upgrade to the 16 bit
bus, reprogramming would be negligble.

I missed the discussion leading up to Wetter's article, but as someone who
avidly followed the introductions of the first generation of 16 bit micro-
processors, I felt that his article lacked historical perspective.

Bruce