Article View: comp.sys.ibm.pc
Article #43373Re: Replacing an 80386 with an 80486
From: Ralf Brown
Date: Sat, 03 Mar 1990 01:21
Date: Sat, 03 Mar 1990 01:21
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1660 bytes
In article <9729@portia.Stanford.EDU> dhinds@portia.Stanford.EDU (David Hinds) writes:
} During task switches, the 386 saves its own context, but does not
}automatically save the floating point processor's context. It generates
}an interrupt at the first floating point operation following a task switch,
}so the system software can handle switching 387 contexts. As this feature
}was not present in the 80286, OS/2 probably doesn't know about it. OS/2
Certainly it was present in the 286. From the Intel 286 Programmer's
Reference:
The context of a processor extension (such as the 80287 numerics
processor) is not changed by the task switch operation. ... The
80286 detects the first use of a processor extension after a task
switch by causing the processor extension not-present exception
(#7) if the TS bit is set. (page 11-5)
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!b.gp.cs.cmu.edu!ralf From: ralf@b.gp.cs.cmu.edu (Ralf Brown) Newsgroups: comp.sys.ibm.pc Subject: Re: Replacing an 80386 with an 80486 Message-ID: <8264@pt.cs.cmu.edu> Date: 3 Mar 90 01:21:02 GMT References: <29108@amdcad.AMD.COM> <1640057@hpspcoi.HP.COM> <9830@sequoia.UUCP> <1304@watserv1.waterloo.edu> <9729@portia.Stanford.EDU> Organization: Carnegie-Mellon University, CS/RI Lines: 20