Apache2 x FastCGI x opcode cache

Hi! I have some questions about setting up Apache2/worker and using PHP via FastCGI and using an op-code accelerator. Namely, how do I not confuse the op-code accelerator into re-creating several caches in several memory segments. The webserver in worker mode automatically create (for example) 5 processes that each run many threads. The FastCGI module runs, say 50 processes, and then the php default of PHP_FCGI_CHILDREN is 8. So what does this all add up to? And how does the accelerator group things (Zend ZPS, APC, eAccelerator)? I am not using suexec. All for one website, not a mass-hosting situation. Thanks! -steve--