When did paging get into System V

[Lance Berc]

In article <7878 at brl-smoke.ARPA> gwyn at brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>(Sun
>designed their original memory management hardware to look virtually
>the same as the VAX's, to avoid this.  Not everyone has had that option.)

The memory hardware of Vaxen and Suns (at least twos and threes) are
COMPLETELY different. The only similarity is that Sun-2s support
separate control bits for RW(X?) for both user and supervisor, and
that both have two levels of tables involved in virtual to physical
address calculation. Sun-3s have only two protection bits: read/write
and user/supervisor (just like the 80386...).

Vaxen have both a real-mode (mapping disabled) and TLBs, Suns don't
have either (all references go through the mapping hardware, which is
fast enough to eliminate the need for a TLB, at least on Sun-2s).

Vaxen have page tables in main memory, with pageable secondary page
tables.  Suns have mapping information in specially accessed fast
memory, and have a cache of eight adress space `contexts'. If a Sun
requires a ninth address space then an entire context description has
to be swapped out.

And to ice the cake, Suns even have Reference Bits!

lance

Lance M. Berc			    Phone: (415) 496-6248
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