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Date:      Sat, 26 Jan 2002 00:51:49 -0800
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Nate Williams <nate@yogotech.com>
Cc:        Daniel Eischen <eischen@pcnet1.pcnet.com>, Dan Eischen <eischen@vigrid.com>, k Macy <kip_macy@yahoo.com>, Peter Wemm <peter@wemm.org>, Julian Elischer <julian@vicor-nb.com>, arch@FreeBSD.ORG
Subject:   Re: KSE question
Message-ID:  <3C526E25.3B72F578@mindspring.com>
References:  <3C51D0B6.F6E04EBC@mindspring.com> <Pine.SUN.3.91.1020125164325.24428A-100000@pcnet1.pcnet.com> <15441.56832.170618.611705@caddis.yogotech.com> <3C51E888.FD13A18D@mindspring.com> <15441.59691.361172.394760@caddis.yogotech.com> <3C51F18A.C0D8D6B1@mindspring.com> <15441.62092.864056.841853@caddis.yogotech.com> <3C51F492.CB0FB69E@mindspring.com> <15441.62830.180895.121111@caddis.yogotech.com> <3C51F89E.78DAD01D@mindspring.com> <15441.63876.271856.290838@caddis.yogotech.com> <3C51FF0A.9ACAC316@mindspring.com> <15442.16478.408033.680185@caddis.yogotech.com>

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Nate Williams wrote:
> Again, the issue is that we can't determine *IF* the FPU has been used
> effeciently.  All solutions assume this solution, although Daniel's may
> have a way of short-circuiting this in the short term.

Disable it in the processor when context switching in code
that doesn't have it marked enabled (this can be lazy bound
as well: the default state will be disabled.

When the first access by a program occurs, it will get an
instruction fault.

Handle the fault by setting an "FPU used" flag, and then
enabling it and restarting the instruction.

-- Terry

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