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From: hammond@petrus.UUCP (Rich A. Hammond)
Newsgroups: net.micro,net.arch
Subject: Re: What if IBM used a 68000
Message-ID: <702@petrus.UUCP>
Date: Tue, 26-Nov-85 07:16:04 EST
Article-I.D.: petrus.702
Posted: Tue Nov 26 07:16:04 1985
Date-Received: Wed, 27-Nov-85 05:48:14 EST
References: <212@fas.ri.cmu.edu>
Organization: Bell Communications Research, Inc
Lines: 39
Xref: watmath net.micro:12859 net.arch:2176

> 	IBM tried workstations around both the 8088 and 68000.  While
> ... Customers cast an economic vote for the 8088, not the 68000.
> 
> 	I believe that there were good technical reasons...
> 
	Re: MMU - the 68451 is at least as good as 8088's on board MMU
		besides, it is quite possible to write position ind. code
		with a 68000.  (i.e. no MMU required)
	Re: Virtual Memory - the 8088 can handle page faults?  No way!
		Faulting on segment sized (64k) objects in a 256k
		memory is pretty silly.
	Re: Addressing scheme - Motorola's addressing scheme does not
		force one to do anything in particular.  The use of the
		Versabus was probably to pick up some exisiting boards
		(A/D, ... maybe?).  A sixteen bit data path isn't all
		that expensive, remember, both systems have a 20 bit plus
		address bus.  20 + 8 vs 20 +16
	Re: 8087 support vs Motorola.  I don't believe early PC's came
		with an 8087, by the time the 8087 could have been
		a factor PC's were already well established.  Most software
		ported from CP/M systems didn't use 8087's.
> 
> 	The 68000 had it's chance, with some of the best effort IBM
> could put behind it, and failed to make the impact the PC has for 
> numerous, solid technical reasons.
> 
> 					-John

One other point, which you don't mention, but many do.  The 68000 supports
8 bit peripherals (6800 family chips) with CPU generated E, VMA', VPA'
and with instructions (Move Peripheral Data).  The 6800 family chips
include a nice video display controller, UART, ...  As far as I can see,
the claim that an 8088 supports 8 bit stuff better is pure baloney.

You fail to convince me that the reasons are technical, or solid.
I don't believe that the 68000 had the best effort behind it, marketing
wise, and it was certainly aimed at a different environment than a PC.

Rich Hammond	{ucbvax|allegra|decvax|ihnp4} !bellcore!hammond