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From: david@sun.uucp (David DiGiacomo)
Newsgroups: comp.misc,comp.arch
Subject: Re: Japanese 32-bit micro can be a 68020 or 80386
Message-ID: <53780@sun.uucp>
Date: 19 May 88 00:50:12 GMT
References: <2006@sugar.UUCP>
Reply-To: david@sun.com (David DiGiacomo)
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 21

In article <2006@sugar.UUCP> karl@sugar.UUCP (Karl Lehenbauer) writes:
>There is an article in this week's "PC Week" magazine about a 32-bit micro
>developed in Japan by a joint venture of a couple of major players there
>(sorry, I don't have the article at hand) that has a writable control store 
>and thus can have different microprograms loaded into it to emulate the 80386,
>68020 and others, apparently as a means of getting around microcode copyright 
>issues that have prevented Japanese manafacturers from cloning those processors.
>It's called VM, for Virtual Microprocessor.

The impression I got from reading (vague) articles in EE Times, InfoWorld
and other places is that the VM Systems part will *not* have writable
control store.  As far as I can tell, Shima is designing a 386 clone which
uses PLAs for instruction decoding and sequencing.  The theory seems to be
that this will completely avoid the microcode copyright issue -- writable
control store would just transfer the liability from the IC vendor to the
system vendor.

It's hard to believe that the same micro-machine could efficiently emulate
both the 386 and 68020, microcode or no microcode.

-- 
David DiGiacomo, Sun Microsystems, Mt. View, CA  sun!david david@sun.com