Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!emory!att!linac!midway!ux1.cso.uiuc.edu!uicbert.eecs.uic.edu!uicvm!u39648
From: U39648@uicvm.uic.edu (Darius Vaskelis)
Newsgroups: comp.windows.ms
Subject: Re: IBM's XGA and Windows
Message-ID: <91030.234048U39648@uicvm.uic.edu>
Date: 31 Jan 91 05:40:48 GMT
References: <859@nih-csl.nih.gov> <1991Jan24.132327.8830@gpu.utcs.utoronto.ca>
 <1991Jan28.100703.4680@cc.helsinki.fi> <1991Jan30.045751.3520@disk.uucp>
Organization: University of Illinois at Chicago
Lines: 27

In article <1991Jan30.045751.3520@disk.uucp>, rob@disk.uucp (Rob Miracle) says:
>Simple, the XGA adapter is a BUS master microchannel card.  Bus mastering is
>only supported under 80386 processors.

Whoa!

Bus-mastering is a function of the BUS, not the processor.

When IBM introduced a 16-bit expansion bus on the PC AT, they even added a very
simple (not terribly high performance) provision for bus-mastering adapters!
The original PC AT used a 6MHz 80286.

Or what about the IBM PS/2 Models 50 and 60 and the current counterpart, the
50Z?  They are all 16-bit Microchannel machines that allow for full bus-
masters!  All three are based on a 10MHz 80286.  IBM even makes a few 16-bit
Microchannel full bus-mastering adapters: the Image Adapter/A and the
extremely high-performance SCSI Adapter/A.

Microchannel architecture is not "linked" to Intel's iAPX86 processor
family in any way.  Neither is the concept of bus-mastering.  Note the IBM
RS/6000 workstations, they use the i860 RISC chip for the CPU, and almost
every Microchannel adapter designed for it it a full bus-master.

- Darius
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