- RAM: random access memory.
| Transistors per bit | Relative access time | Persistent | Sensitive | Relative cost | Applications | |
|---|---|---|---|---|---|---|
| SRAM | 6 | 1x | yes | no | 1000x | Cache memory |
| DRAM | 1 | 10x | no | yes | 1x | Main memory, frame buffers |
Practice:
DRAMs and SRAMs are volatile in the sense that they lose their information if the supply voltage is turned off.
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Nonvolatile Memory:
- Rom: read-only memory. but even though some types of ROMs can be written to as well as read. For example: PROM, programmable ROM; EPRROM, erasable programmable ROM; EEPROM, electrically erasable PROM;
- Flash memory, based on EEPROMs.
- SSD, solid state disk.
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Accessing Main Memory
- bus: data flows back and forth between the processor and the DRAM main memory over shared electrical conduits called buses.
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Disk: disks are workhorse storage devices that hold enormous amounts of data.
DRAM and disk performance are lagging behind CPU performance.
Practices: