From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] authorization schemes (was CORBA)
From: forsyth@vitanuova.com
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Message-Id: <20011001105539.2CE0B19ABD@mail.cse.psu.edu>
Date: Mon,  1 Oct 2001 12:00:10 +0100
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> According to some of the Berkeleyites, there was a flaw in
> the VAX-11/750 memory management unit (microcode?) such
> that they were unable to use copy-on-write.

perhaps early 750s had a bug that instructions wouldn't
restart correctly on protection trap, which would prevent emulating
the page-modified bits (i haven't got a vax handbook to hand but
i think those were the bits missing from the page tables), in order
to do copy-on-write, but if the broken hardware would support
any form of paging on the platform, it must have been able
to support copy-on-reference (ie, instructions could be restarted
after page-invalid traps).

mind you, the 750s i had seemed fine with c-o-w.