On 2001-Jan-17 10:43:10 -0500, Garrett Wollman <[EMAIL PROTECTED]> wrote:
><<On Wed, 17 Jan 2001 14:26:54 +1100, Peter Jeremy <[EMAIL PROTECTED]> said:
>
>> To support multiple masters, you need proper locks.
>
>On older processors, yes. On processors with the CX8 feature bit set,
>you can do it without any sort of locking (indeed, this is a primitive
>that semaphores can be built upon).
This particular sub-thread was specifically discussing the 80386 - as I
thought was clear from the context. I am aware of the CMPXCHG8B insn,
but it's not relevant to the 386 or 486.
>On pre-Pentium processors (which lack the CX8 feature) this sort of
>sequence is impossible. OTOH, I don't think SMP works on any
>pre-Pentium processor, so again this degenerates to:
There are SMP machines using both 386 and 486 processors. There is
no support in FreeBSD for SMP on pre-Pentium processors.
Peter
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