spc:
:Well, that's because on the VAX (to bring classic computers into
:this) had an ENQUEUE and DEQUEUE (I think those are the mnemonics)
:instructions which handled double linked lists (of which queues and
:stacks can be built out of).
*sigh* never mind. did anyone ever use the polynomial evaluators, too?
:Why the need for PALcode to do that on the Alpha is a bit odd - all
:you really need is an instruction that does an atomic "test and
:set" to ensure atomicity (hmmm, it could be that instruction they
:added, although it seems strange because DEC Unix supports multiple
:CPUs and you NEED that for multiple CPUs).
test and set can ensure serialisation, but not atomicity. if the os
isn't counting what other processors are accessing its memory, it needs
atomicity because the serialisation won't be listened to. however,
doubly linked lists are one of a class of things that can be tackled
with a two-word compare and swap instruction (as on the 680x0) - see the
synthesis description for actual algorithms, url unknown, sorry - which
makes them atomic. we'll dig out the pages and post the algorithms if
you wish (if they aren't too self-referential).
--
Communa (together) we remember... we'll see you falling
you know soft spoken changes nothing to sing within her...
Received on Wed Mar 18 1998 - 14:19:23 GMT