12. SMP.

Ouaich, SMP is supported, and I am sure that ROSS's dual CPU modules are supported as you can see by yourself:

piou@ywing:~ > cat /proc/cpuinfo 
cpu             : ROSS HyperSparc RT625 or RT626
fpu             : ROSS HyperSparc combined IU/FPU
promlib         : Version 3 Revision 2
prom            : 2.25
type            : sun4m
ncpus probed    : 2
ncpus active    : 2
Cpu0Bogo        : 125.33
Cpu1Bogo        : 125.33
MMU type        : ROSS HyperSparc
invall          : 0
invmm           : 0
invrnge         : 0
invpg           : 0
contexts        : 4096
CPU0            : online
CPU1            : online
piou@ywing:~ > 

The SparcStation 10 and SparcStations 20 are SMP capable machine and according to the FAQABOSS the following combinations are known to work :

• 2xSM40 ( model 402 )
• 2xSM41 ( model 412 )
• 2xSM51 ( model 512 )
• 2xSM512 ( model 514 )
• 2xSM61 ( model 612 )
• 2xSM71 ( model 712 )
• 2xSM81 ( model 812 )

And, as stated earlier, CPU modules in SparcStations 10 and can run a different clock speeds, the following ones __SHOULD__ work:

• 2xSM50
• SM41, SM51
• SM41, SM61
• SM51, SM61
• SM71, SM81

If you want to learn more about SMP and Linux you can read the SMP-HOWTO

How does it performs? Well, it is fast, really fast. Some of the java Demos can run faster on a dual HyperSparc 125Mhz 128MB ( ywing ) than on a dual celeron BP6 433@433Mhz 192MB ( calimero ). The same applies for the Gimp. When it comes to compiling calimero runs faster than ywing. Both computers running 2.2.16 kernel and calimero's hard disk subsystem is full SCSI.

One important detail when you plan to have different CPU modules in your computer is to have the same kind of modules, you cannot mix SuperSparc and HyperSparc for example, but you can have an odd number of CPUs, for example 3. They are said to be able to run modules at different clock speed as written in this article form AcesHardware , but I have not witnessed it.

I plan to upgrade ywing to 4 CPU in order to see how the performance scales.