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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.freebsd.misc,comp.unix.bsd.netbsd.misc
Subject: Re: Curious about *BSD History
Date: Fri, 05 Jul 1996 12:58:58 -0700
Organization: Me
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Message-ID: <31DD7402.656B7335@lambert.org>
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Ignatios Souvatzis wrote:
] > ] FreeBSD has added optional pmap entry points to support
] > ] microcoded TLB's better.
] >
] > This hurts, I think, in the non-microcoded TLB case (Alpha, PPC).
]
] PPC 603 _have_ microcoded TLBs.
BeBox has 2 601 with no L2 cache and use the cache circuitry for
MEI (instead of MESI) cache coherency.
I don't think you can safely use the (fewer than on the 603) 601
features and maintain coherency.
I could be wrong; I haven't got a BeBox yet.
Nevertheless, the point is valid, even if I am wrong about all
models of the PPC (my gut says I am not), in that the trade here
is for increased overhead on exactly those systems which can not
afford it. You want a soloution which trades overhead for hardware
assistance: the bias should be toward systems without the microcoded
TLB's.
Regards,
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.