Patrik:
If you want to do the filtering type applications on an 8051 derivative I suggest that you look at the highest MIPS parts available. It is commom that real time filtering applications require several buffers of size large enough so as to require an XDATA memory space as opposed to internal memory space. Filter algorithms also require visiting all locations in the buffers so it is important to allow yourself as wide of bandwidth as possible (i.e. reduce the uSec/byte you spend at each buffer element) to permit the real time throughput of the system to be met.

It is also my experience that non-DSP type microprocessors that manufacturers have targeted at certain DSP type filtering applications have a special type of register set, and applicable assembly language instructions, called a MAC. This MAC (multiplier and accumulator) is a feature not found on the 8051 derivatives I have looked at.

Michael Karas