[bayindirh]

Depends on the hardware and what you are making with that hardware. Some processors can do complicated things stupidly fast (e.g. when SIMD done right), and for some hardware platforms, a mundane operation can be very costly since they are designed for other things primarily.

My favorite story is an embedded processor which I forgot its ISA. The gist was, there was a time budget, and doing a normal memory access would consume 90% of that budget alone. The trick was to use the obscure DMA engine to pump data into the processor caches asynchronously. This way, moving data was only ~4% of the same budget, and they have beaten their performance targets by a large margin.

[bobmcnamara]

I've run into this on PowerQuicc network processors. It was so handy having the packets(or at least header) dropped straight into the cache