Date: Tue, 5 Aug 1997 17:04:59 -0400 (EDT) From: Peter Dufault <dufault@hda.com> To: ejs@bfd.com (Eric J. Schwertfeger) Cc: mal@kairos.algonet.se, chat@freebsd.org Subject: Re: Make this a relese coordinator decision (was Re: ports-current/packages-current discontinued) Message-ID: <199708052104.RAA20655@hda.hda.com> In-Reply-To: <Pine.BSF.3.95.970805142026.9281C-100000@harlie.bfd.com> from "Eric J. Schwertfeger" at "Aug 5, 97 02:21:40 pm"
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> > (*) Or was it _two_ of them? I have some faint memories they had to use > > two to make it work with a multi-process os. > > If I remember right, the 68010 had a limitation that made it difficult to > deal with page faults, so the second 68010's purpose was to take care of > page faults, then let the primary 68010 continue. If I remember correctly the 68000 had the problem that it could only restart instructions and systems such as the old Masscomp had two 68000s, one to continue faulted instructions. The 68010 added info to the stack frame to permit instruction continuation. The problem has to do with instructions such as can be dramatized by: > *page_fault_location = *io_register_with_nasty_side_effect; where you need to be sure io_register isn't de-referenced twice. Peter -- Peter Dufault (dufault@hda.com) Realtime development, Machine control, HD Associates, Inc. Safety critical systems, Agency approval
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