>> 
>> So what's going on? I don't think the 'we just have a better os' really 
>> cuts it as an explanation :=)
>
>Solaris does have the overhead of "true" multiprocessing.  

Yep. Insanely so. To the point of using LDSTUB (atomic load/store
unsigned byte) in machine dependent code on platforms that can
*never* be MP (sun4c). Atomic instructions cause a flush of
write buffers and a halt of SBus activity.

I really don't think that Solaris could be taken as a sane example
of what "true" multiprocessing should be. A much better example would
be sorta like early SGI variant kernels I saw at Kubota (Ardent):
one atomic operation (spinlock, with h/w timeout/death) and a P/V semaphore
built on top of that to replace/supplement sleep/wakeup. Period.

Solaris, instead, reads like an academic text of all possible multithreaded
operations: semaphores, condition variables, reader/writer locks, mutual
exclusion locks, bozo variables (operation to check with Platforms and Systems
Architecture Review Committee as to whether the desired operation
is "sound")... but I digress.. oops. sorry. Gotta go get coffee...much
too early......:-)