V22.0436 - Prof. Grishman

Lecture 24:  Input-Output

Memory -- final notes:

Virtual memory

Virtual memory provides the next step in the memory hierarchy after main memory: disk memory. The gap in access times, however, is much larger (between 100ns main memory and 10ms disk access time) and this affects the parameters of the design (pages are much larger than cache lines, and hit ratios must be much higher for the machine to work efficiently). As technology changes, we can expect the parameters of the memory levels to change, but the basic idea of a memory hierarchy to remain.


Input-output: needs

Input-output: bus organization

Asynchronous transfer

Spring 1999