Embedded Systems Design, 2nd Edition

68 Embedded systems design

the RISC solution requires twice as much program storage which

means twice the memory cost and power consumption (this is a bit

of a simplification but the increase is very significant). And yes,

this argument is very similar to that put forward when the first

microprocessors appeared where memory was very expensive

and it was advantageous to uses as little of it as possible — hence

the CISC architectures.

ARM's solution to this was to add a new set of instructions

to the instructions set called the Thumb instructions. These are

reduced in functionality but are only 16 bits in size and therefore

take less space. As the processor ...