Dual Processor Usage on 3B2/700

[John Roberts]

In article <839 at ambush.UUCP>, kimcm at ambush.UUCP (Kim Chr. Madsen) writes:
> 
> Does anybody have some information about the dual processor usage on
> the 3B2/700?  Does the OS support using both processors for common
> applications or is it necessary to compile the applications
> specifically to utilize the extra processor, like on the 3B2/600 with
> dual-processor option?

I have never heard of any application requiring recompilation to be able
to use the MPE (Multi-Processor Enhancement) on the 600 or 500.  The only
program that broke, as far as I know, was Oracle, because of some funky
stuff with the cache descriptor table.  It's fixed now.

With the MPE you get some utilities, which make the second processor known
to the kernel.  It should be (IS, in my experience) completely transparent
to your application.  Before you add the MPE, you should do some sar checking
to make sure that the application is not I/O or system call bound, otherwise
the MPE won't buy you anything.  I have some more precise metrics, if anyone
needs them.

BTW, the 700, and the 600/500 with an upgrade to the 22MHz system board,
can support multiple MPE's - up to four on the 700 and 600, two on the 500.

> Second, how well does the 700 perform compared with a 600?

The base CPU is about 25% faster.  You might want to factor in the larger
RAM space, if it's important.  Each MPE gives diminishing returns; the 3B2
is rated (AT&T MIPS ONLY - NO FLAMES PLEASE) as follows:

	3B2/600 no MPE	- 4.0 MIPS
	3B2/700 no MPE	- 5.0
		1  MPE  - 7.5
		2  MPE  - 8.5
		3  MPE	- 9.0
		4  MPE	- ?

but the actual numbers are HIGHLY application dependent.  Note that no
number is given for the fourth MPE, since it adds power only in very
specialized cases.
 
If you have a program that can't use the MPE without recompilation, I'd
really like to hear about it.

> Kim Chr. Madsen, AmbraSoft A/S, Rojelskaer 15, DK-2840 Holte (Denmark)
> UUCP: kimcm at ambush.dk, PHONE: +45 2807 522, FAX: +45 2423 090

John M. Roberts            AT&T Canada  Vancouver  BC
(604) 689-8911             {alberta,uw-beaver}!ubc-cs!attvcr!jroberts
What! Me Worry?		   attmail!jmroberts

PS: oli.3b is invalid here, and probably throughout NA, so I dropped it.