Just another point to consider... If I am not mistaken, Oracle behaves diffirently on "multi-headed" systems versus "single-headed" but I don't remember whether this is accounted during linking or via _cpu_count parameter. At least, latching must be different.
ANYWAY, does anyone know how Oracle would or should handle the _CPU_COUNT and the continuously variable CPU allowance? I still don't exactly how the APV Hypervisor determines what a tenth of a CPU is, but I'm thinking that _CPU_COUNT won't take decimals or fractions. I've found a possible vague reference to this in licensing at http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/FQ114190 but nothing regarding performance and init.ora parameters.
-- Best regards, Alex Gorbachev