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Path: utzoo!watmath!clyde!rutgers!husc6!ddl
From: ddl@husc6.UUCP
Newsgroups: comp.os.minix
Subject: Re: Which clones *don't* run MINIX
Message-ID: <1192@husc6.UUCP>
Date: Mon, 9-Feb-87 02:00:00 EST
Article-I.D.: husc6.1192
Posted: Mon Feb  9 02:00:00 1987
Date-Received: Tue, 10-Feb-87 05:09:50 EST
References: <275@ihnp3.UUCP> <459@moncol.UUCP> <2529@well.UUCP> <172@axis.UUCP>
Organization: Harvard University, Cambridge MA
Lines: 36
Keywords: MINIX BIOS COMPATIBILITY

In article <172@axis.UUCP>, philip@axis.UUCP writes:
> This is explained in the book.
> It is also almost certainly explaine if you have ever tried to use
> BIOS calls yourself - certain of them can only be used in certain
> circumstances, and others leave the machine in an unstable state, which
> must be rectified by making another BIOS call (with parameters set so that
> it does nothing) to make the machine stable again ....

	I use the BIOS calls a great deal and I have never encountered
problems with the machine being left in an unstable state. Can you give
a specific example?

> But, the most important reason (as given in the book) is that the BIOS
> calls do not use interrupts. So, when your shell does a read(), BIOS
> loops on the status bit of the serial line UART (for example), and the
> machine effectively stops for all other processes.

	This is plain wrong.  The IBM PC keyboard is interrupt-driven.
Int 9 is used, if you are interested.  Characters are stored in a FIFO
buffer.  The get-a-character call does, indeed, loop waiting for a
character to appear in the FIFO buffer; however, there is a get-status
call which will not hang.  Furthermore, it is trivial to catch int 9
and use it as a cue to ckeck for keyboard activity.  The combination
gives you an interrupting keyboard.

> BIOS/MSDOS/PCDOS and the rest realy are single process machines,
> and in general, no part of them is useful in a 'real' computing
> environment.

	I use the BIOS in OS for keyboard and disk i/o.  It works fine.
It runs on clones because they all emulate the BIOS interface.
I like to think of it as a "'real' computing environment."  Well, as
real as you can get on an 8088.

						Dan Lanciani
						ddl@harvard.*