how is it possible to render with multiple cpus on a single frame?

That pretty much happens when you hit render, if you have a multi-core setup.

Or with CPUs, do you mean multiple machines? That would be network rendering.

im just talking about multiple cores.

according to this though that doesn't happen
http://odforce.net/wiki/index.php/FrequentlyAskedQuestions#Q:__How_does_Houdini_use_multiple_CPUs_or_cores.3F_Does_it_multithread.3F [odforce.net]

it says you have to launch mantra with an extra string.

It says to me that you only need to use a special option if you want to do MultiProcessing. Nothing special needs to be done to use all the cores on your computer (multithread).

ok cool. thanks.

now that i think about it, i should have a go at getting my other quad core working with this.

i found on this page http://odforce.net/wiki/index.php/MantraRemoteRendering [odforce.net]

you can use mantra -H host1,host2
how do i get to the command line?

the mantra rop has a command line in it's parameters, mantra allready is there , just add You stuff their