Messages in this thread | | | Date | Thu, 06 Mar 2008 09:18:56 -0800 | From | "H. Peter Anvin" <> | Subject | Re: RELEASE BLOCKER: Linux doesn't follow x86/x86-64 ABI wrt direction flag |
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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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