[SunRescue] help with CPU ID

[James Lockwood]

On Thu, 16 Sep 1999, Gregory Leblanc wrote:

> Isn't solaris7 heavily optimized for the Ultra Sparc (64-bit) SPARC Cpus?
> Just something I'd heard tossed around someplace.

The 32-bit Solaris 7 kernel performs comparably on SPARC V8 (sun4m/sun4d) 
CPU's and V9 CPU's (sun4u).  UltraSPARCs accelerate some functions through
special instructions (memcpy/bcopy being good examples, they are handcoded
using VIS instructions), but the majority of the OS will scale with
overall processor speed regardless of architecture.

> Why not the SM51?  Isn't that a 50Mhz CPU with 1 meg of cache?

Yes, but the mbus must always run slower than the CPU speed when the CPU
has e-cache.  The SM41's escape this limit as they technically run at
40.3MHz, allowing a 40MHz mbus speed.  SM51's run at exactly 50MHz so the
50MHz mbus speed in the SS20 can't be used, only the 40MHz mbus.  A
SS20/51 and a SS10/51 will both run with a 40MHz mbus and will perform
identically.

It boggles my mind that Sun ever sold the SS20/51[1,2,4], as it doesn't
really buy you anything over a similar SS10.  The SM50 doesn't perform as
well in MP applications due to memory contention, but it was a heck of a
lot cheaper to build than the SM51 and performs about as well in a
single-CPU configuration.

-James