Computers as Components, 2nd Edition

4.3 I/O Devices 169

SIMMs and DIMMs

Memory for PCs is generally purchased as single in-line memory modules

(SIMMs) or double in-line memory modules (DIMMs). A SIMM or DIMM is

a small circuit board that fits into a standard memory socket. A DIMM has two sets

of leads compared to the SIMM’s one. Memory chips are soldered to the circuit

board to supply the desired memory.

4.2.3 Read-Only Memories

Read-only memories (ROMs) are preprogrammed with fixed data.They are very

useful in embedded systems since a great deal of the code, and perhaps some data,

does not change over time. Read-only memories are also less sensitive to radiation-

induced errors.

There are ...