Memory capacity expansion
- main memory, main memory, also known as internal memory
- The capacity of the memory chip is limited. In order to meet the actual memory capacity requirements, the memory needs to be expanded.
- Main memory expansion: connecting memory chips together to form sufficient capacity
- The main methods of memory capacity expansion are:
bit extension: Only increase the word length , and the word number of the memory is consistent with the word number of the memory chip, and use a common chip select signal for all chips;
word expansion: Only expanded in the word direction, while the number of bits remains unchanged. The chip select signal is required to distinguish the addresses of each chip.
grapheme extension: The capacity of a memory is assumed to be M×N bits. If a l×k-bit chip is used (l<M, k<N), it needs to be expanded in both the word direction and the bit direction. At this time, a total of (M/l)×(N/k) memory chips are required.
Bit extension, word extension, and word bit extension usually involve the calculation of the required address lines and data lines. Let's look at an example first:
Let's look at another example:
bit extension
Example: Two 1K X 4-bit chips can form a 1K X 8-bit memory ( 4-bit→8-bit )
word expansion
Example: Two 1K X 8-bit chips can form a 2K X 8-bit memory ( 1K→2K )
grapheme extension
Example : 1K _ _ _ _ _ _ _ _
