Ask A Scientist© Computer Science Archive

Index Key:   COM031
Author:      carol a jackson
Subject:     Computer size measurement.

What is the measurement for speed in a computer?
What is the measurement for capacity in a computer?

Response #:  1 of 1
Author:      asmith
Measurements for speed are called "benchmarks", but they are often not
representative of the speed you will get. If you look at the MHz rating that
gives you a rough measure, but a 50 MHz can be much faster than a mhz 
computer for certain problems.

Capacity is measured in bytes (mostly Megabytes nowadays) - one byte is
roughly one character of text, and 4 bytes is the usual size for instruc-
tions and more complicated data.

There are a variety of capacities you need to worry about, if you are also
concerned about speed.  Many CPU's have what is called "cache" memory, and
nowadays can have several levels of cache -- what is important for this is
both the capacity and the speed.  Regular RAM memory is slower than the
cache, and much bigger (usually 4-8 Megabytes on PC's, up to 100's of
Megabytes for really fast CPU's).  And then there is the long-term data
storage, or disk and tape space, which is usually 100's to 1000's of
Megabytes.