🚀 go-pugleaf

In article <1992Sep11.121830.17069@hubcap.clemson.edu> zilla@nj.nec.com (John Lewis) writes:
>Someone told me that the SGI multiprocessor machines cannot run
>different unix processes on different processors; they can only
>run a single (but possibly parallelized) process at a given time.

Someone told you very wrong.  All processors peruse the run queue.
Any process runs on any processor unless you explicitly assign
a process to a processor and/or restrict a processor to run only
certain processes.

>The reason was said to be that the machines do not implement
>any mechanism for simultaneous writes.
>
>Is this correct?  If so, how are simultaneous writes from
>different threads of a parallelized process prevented?

Simultaneous writes from different threads of a parallized process
are not prevented.  (Threads are known to the kernel and each
has its own pid, kernel supported stack, etc).  Harware spinlocks
are avaliable to user-level programs directly or through a couple
of different MP programming interfaces to provide serialization
if that's desired.

Bent