Introduction
There are two main types of processor used. They are CISC, and RISC.
RISC
RISC stands for Reduced Instruction Set Computer
It has only a few essential built in instuctions
Each instruction can be completed in a single clock cycle
More lightweight power efficient devices might use these, such as mobile phones
Benefits
- Lower power consumption
- Pipelining is possible, as one instruction is exactly one clock tick
- Simple set of commands
- Faster output due to the simplicity of instructions
Drawbacks
- More RAM usage due to more instuctions overall
- Harder and more work to compile to, as less instructions make it harder for complex tasks
An example of a RISC instruction to multiply 2 number together would be:
LDA R1, X
LDA R2, Y
MUL R1, R2
STO R1, X
CISC
CISC stands for Complex Instruction Set Computer. These have a huge amount of instructions in comparison to RISC, which brings some benefits, though also a few drawbacks.
Benefits
- Fewer Assembly Language instructions needed as built in instructions can do more
- Most built in instructions are simple
- Less RAM is required, as code is shorter
- Compiler has to do less work
Drawbacks
- More expensive to produce
- Many specialised instructions exist, though unused by many programs
- Uses much more power than RISC to run
An example of a CISC instruction to multiply 2 numbers together is:
MUL A, B