Width: 1 bit, 4 bits (a nibble), 8 bits (a byte), or 16 bits (a word), and so on.
Depth: How deep the chip is: 256 KB, 1 MB, 4 MB, 8 MB, 16 MB, 32 MB, and so on.
By combining the depth and width, the "size" of the DRAM chip can be determined.
Here are a few points to remember when specifying DRAM:
When upgrading memory, you add megabytes.
When purchasing DRAM, you buy bits.
Calculate chip size by multiplying depth by width; the result is measured in bits.
One KB of memory is equal to 8192 bits (1024 x 8).
One MB is equal to 8,388,608 bits (1024 x 1024 x 8).
The following table lists common DRAM module sizes.
| Chip (depth x width) | Number of Chips/Module | Memory per Module |
|---|---|---|
| 256 KB x 1 | 8 | 256 KB |
| 256 KB x 4 | 2 | 256 KB |
| 256 KB x 16 | 1 | 512 KB |
| 512 KB x 8 | 1 | 512 KB |
| 1 MB x 1 | 8 | 1 MB |
| 1 MB x 4 | 2 | 1 MB |
| 1 MB x 16 | 1 | 2 MB |
| 2 MB x 8 | 1 | 2 MB |
| 4 MB x 1 | 8 | 4 MB |
| 4 MB x 4 | 2 | 4 MB |
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