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Message-ID: <47D02780.4060309@zytor.com>
Date: Thu, 06 Mar 2008 09:18:56 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Robert Dewar <dewar@...core.com>
CC: NightStrike <nightstrike@...il.com>,
Olivier Galibert <galibert@...ox.com>,
Chris Lattner <clattner@...le.com>,
Michael Matz <matz@...e.de>,
Richard Guenther <richard.guenther@...il.com>,
Joe Buck <Joe.Buck@...opsys.com>, Jan Hubicka <hubicka@....cz>,
Aurelien Jarno <aurelien@...el32.net>,
linux-kernel@...r.kernel.org, gcc@....gnu.org
Subject: Re: RELEASE BLOCKER: Linux doesn't follow x86/x86-64 ABI wrt direction
flag
Robert Dewar wrote:
>
> Sounds good, but has almost nothing to do with the real world. I
> remember back in Realia COBOL days, we had to carefully copy IBM
> bugs in the IBM mainframe COBOL compiler. Doing things right and
> fixing the bug would have been the right thing to do, but no one
> would have used Realia COBOL :-)
>
> Another story, the sad story of the intel chip (I think it was
> the 80188) where Intel made use of Int 5, which was documented
> as reserved. Unfortunately, Microsoft/IBM had used this for
> print screen or some such. Intel was absolutely right that
> their documentation was clear and it was wrong to have used
> these interrupts .. but the result was a warehouse of unused
> chips.
IBM used it for print screen (and other calls), because Microsoft
cassette BASIC used all the non-reserved INT instructions as byte codes
(they cut it down to *only* half the interrupt vectors in the disk version.)
We're still stuck with the consequences of that hack.
-hpa
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