[geeks] UltraSparc IV dual core?

[Scott Howard]

On Thu, Jan 16, 2003 at 09:14:14PM -0700, Chris Byrne wrote:
> I wonder how these dual cores look to older os's that don't know about
> them vs newer ones. 

Umm.. no comment

> Can/are the newer OS's be programmed to take advantage of the inherent
> design advantges of having the dual core (speed of transport, coherency
> etc...), and if there is a significant difference in performance using
> existing os's between a conventional SMP implementation and a multicore
> implementation.

Yes, and not really.  There are some differences with respect to access
times to cache/memory/etc, but thats about all - and these are things
which we're already seeing (to a lesser extent) with existing systems.

A number of parts of existing US-III systems work on 2 CPUs - the most
noticeable being the Dual Cheetah Data Switch (DCDS) which as the name
implies controls pairs of CPUs, and has short-cut data/address paths between
the pair. Fuatures such as Solaris 9 9/02's MPO (Memory Placement
Optimisation) where the OS attempts to run processes on a CPU which is
"close" to where it's data is in memory are also a start on support forsuch
processors.

As with all new OSes there will almost certainly be compiler optimisations
for the new CPUs (as there were for US-III, US-III, US-I, etc) which will
improve performance on the new CPUs, but I'd be fairly certain backwards
compatibility will be maintained - as it always has been (for apps at
least - dont expect to run Solaris 2.5.1 on the new CPUs :)

That's about all I can say with NDA's :)

  Scott
  (Speaking for me, not my employer)