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From: davidsen@steinmetz.UUCP (Davidsen)
Newsgroups: net.micro,net.micro.pc
Subject: Re: IBM's new 32 bit machine - not an 80386?
Message-ID: <354@steinmetz.UUCP>
Date: Tue, 7-Jan-86 12:54:44 EST
Article-I.D.: steinmet.354
Posted: Tue Jan  7 12:54:44 1986
Date-Received: Thu, 9-Jan-86 05:58:03 EST
References: <216@utastro.UUCP> <210@ism780c.UUCP> <399@l5.uucp>
Reply-To: davidsen@kbsvax.UUCP (Davidsen)
Organization: GE CRD, Schenectady, NY
Lines: 42
Xref: linus net.micro:12205 net.micro.pc:6216
Summary: 

In article <399@l5.uucp> gnu@l5.uucp (John Gilmore) writes:
>In article <216@utastro.UUCP> jk@utastro.UUCP (John Krist) writes:
>>     I have been informed by someone that the IBM 32 bit machine does not
>>  use a 80386.  But I was assured by the person I talked to from IBM that 
>>  the computer will run PC software.
>>                      What's going on?
>
>The obvious answer is that it could have an 8088 (or 80286) and some other
>processor, probably the RISC chip that grew out of the IBM 801 research
>machine.  Of course, IBM always tells *me* what they're doing...  :-)
>
>Software emulation would work OK too, especially if the processor is fast
>enough.  I suspect a 68020 can emulate an 8088 faster than the 8088 (though
>I haven't tried it).

Jan 86 Dr Dobb's Journal had an article on emulating an 8080 using a 68K, and
even with a few compromises the emulation doesn't run very fast (usefully
fast, but only about 1.4MHz effective speed). There are (at least) two things
the 68K doesn't do well, namely decimal arithmetic and segmentation. The lack
of the "half carry" flag in hardware requires a bunch of emulation, as does
the action of the segmentation.

Without getting into the issue of segmentation vs. linear addressing, the 8088
does segmentation *really well*, and a completely correct emulation will
probably not run "faster than the 8088". Note that I, too, have not tried it,
but I believe that there is an "add on" to the 8088 emulation on the Amiga
(don't flame me if it's the Atari) machine.

There's no doubt that the 68020 could run the 8088 code fast enough to be
useful, and I have a great Z80 emulator in C which will run (eventually) on
almost anything, perhaps I could run CP/M under the MS-DOS version of the
emulator, under the 8088 emulator... then again I could just use a coprocessor
board or get some up to date software.
-- 
	-billd
	seismo!rochester!steinmetz!        unirot
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ihnp4!                              crdos1!davidsen
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        chinet! -----------------/

"It seemed like a good idea at the time..."