[rescue] What to do with the SS20

[Sandwich Maker]

" From: Steven M Jones <smj+rescue at crash.com>
" 
" On 06/22/2014 06:21 AM, Sandwich Maker wrote:
" > from memory, the reason for 4.1.4 was
" > integrating the ross kernel fixes as sun started selling ross-equipped
" > ss20s, and i believe it supports smp on rosses.
" >
" > it also supports smp on ti cpus, afaik something sun never advertised.
" > i personally tested and verified this.
" 
" Sun introduced multiprocessor support in SunOS 4.1.2, IIRC, partly in
" response to Solbourne (IMHO). The SPARCserver 600MP models were out and
" 4.1.2 supported them well before the first harrowingly unstable Solaris
" 2 release, so I don't think the MP support was a secret.

yes, but it didn't run on ss20s or ross cpus.  i'm curious if it runs
on the sparc powerup enhanced sun4c, or only proper sun-branded cpus.

" Also, I believe all SunOS 4 releases can only have one CPU executing
" kernel code at a time. I'm not sure if technically you have to call that
" asymmetric multiprocessing, rather than SMP.

now that you mention this, i think you're right.  it wasn't a problem
for ${WORK[1995]}, as we were doing complex fpga layouts and sims, and
2 cpus meant the engineers - and the systems - could do useful work on
one cpu while the big heavy sim app hogged the other one.

dredged out of 2-decade-old memories, solbourne dug into the kernel
code and implemented fine-grained spinlocks, but sun basically just
put one giant spinlock around the entire kernel.  since solbourne
licensed sun's codebase, why couldn't sun just build on their work?
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh at an.bradford.ma.us                       and think what none thought