The first versions of the PS3 has 10 CPUs, with one turned off.
The 10 are:
1 PPE
8 SPE
1 PS2 EE CPU
With one SPE turned off for higher yield, and another SPE used for
the security, then that means you still have 8 CPUs to work with.
Maybe it is possible to free up the SPE for security and get 9 CPUs.
I think after the emulation of the PS2 via software gets better the
later versions of the PS3 will have the PS2 chip removed, unless
Sony can't get the emulation right and keeps it in there forever.
In that case they may open up the API for the PS2 chip and it can
be used as an extra CPU (maybe for music or drawing the main
character, etc). But if they do remove it in later versions of the
PS3, those running Linux or those wanting to write homebrew via
the XMB may want to get the first version of the PS3 as you can access
that extra PS2 CPU.