cvs commit: src/sys/i386/i386 pmap.c

Peter Jeremy PeterJeremy at
Wed Nov 10 10:53:16 PST 2004

On Tue, 2004-Nov-09 12:19:54 -0800, Alfred Perlstein wrote:
>* Stephan Uphoff <ups at> [041109 10:43] wrote:
>> Caugh, caugh ... yes that would be a fine name .... caugh, caugh 
>Don't feel too bad, the original spl mechanism would talk to the
>hardware, what you mentioned was an optimization that spl didn't
>get until later.

The SPL mechanism was an excellent fit for the PDP-11 (and M68K) which
managed interrupt priorities within the CPU.  On the PC, it was far
more expensive because interrupt prioritisation was managed in the
i8259's and required several io instructions to update.  Moving to a
software SPL was effectively just moving back to the PDP-11 approach
(managing priorities within the CPU) though with the prioritisation
explicitly coded rather than in the microcode.

Peter Jeremy

More information about the cvs-all mailing list