Memory subsystem
The memory subsystem is an addressable sequence of storage locations containing instructions and data for use by the processor as it executes programs. Modern computer systems and digital devices often contain over a billion 8-bit storage locations in main memory, each of which can be independently read and written by the processor.
As we saw in Chapter 1, Introducing Computer Architecture, the design of the Babbage Analytical Engine included a collection of axes, each holding 40 decimal digit wheels, as the means of storing data during computations. Reading data from an axis was a destructive operation, resulting in zeros on each of an axis’s wheels after the read was complete. This was an entirely mechanical method of data storage.
From the 1950s to the 1970s, the preferred implementation technology for digital computer memory was the magnetic core. One bit of core memory is stored in a small toroidal (donut-shaped) ceramic permanent magnet. The set...
