a) Faster clock (less time between steps) - measure in GHz or MHz
     more difficult and more expensive to make faster cpu's.

b) Wider Bus (transfer more information to/from memory) - 16 bits/32 bits/64 bits/128
    more lines takes more space in the IC which could be used for other things.

c) Cache Memory (try to save important information in faster memory)
    use a small, very fast memory, very close to cpu
    takes space, more expensive
    hopefully you will find information on the cache most of the time.

d) Multiple CPU's
    two or more CPU's (duo systems, quad systems)
    not all problems can be done faster with more CPU's

e) different design
    different machines

Comparing some Microprocessor chips:

Intel

Server	Desktop	Laptop
Itanium 2 - multi processor	Pentium Extreme	Pentium M
Xeon - multi processor	Pentium Celeron	Mobile Celeron
Pentium D