It depends on if the DSP is in use. In OS2007, yes, it was always at 333 MHz regardless of the state of the DSP.

In OS2008, it depends. With the default OP Mode set by OS2008, when the DSP is not in use (i.e. you don't have Media Player running), then the frequency is 400 MHz; however, if the DSP is in use, the CPU will go down to 400 MHz while the DSP goes up to 133 MHz. The OP Mode is really a fancy way of prioritising one over the other: you can modify the kernel to set a different OP Mode in which the DSP will run at half its speed (~66 MHz) while the CPU can still run at 400 MHz. The OP Mode patch allows you to change it on the fly, without having to recompile a new kernel each time. Igor explains one is prioritised over the other in this post: http://www.mail-archive.com/maemo-de.../msg13383.html