Computers as Components, 2nd Edition

176 CHAPTER 4 Bus-Based Computer Systems

4.4.1 Memory Interfacing

If we can buy a memory of the exact size we need, then the memory structure is

simple. If we need more memory than we can buy in a single chip, then we must

construct the memory out of several chips. We may also want to build a memory

that is wider than we can buy on a single chip; for example, we cannot generally

buy a 32-bit-wide memory chip. We can easily construct a memory of a given width

(32 bits, 64 bits, etc.) by placing RAMs in parallel.

We also need logic to turn the bus signals into the appropriate memory signals.

For example, most busses won’t send address signals in row