SDRAM : Computer Hardware Buyers’ Glossary


SDRAM (Synchronous Dynamic RAM) is very high speed RAM (Random Access Memory), 100 up to 200 MHz, the higher the number the faster. Technically it is synchronous memory that works in sync with the system bus, thereby avoiding wait states. It also has an on-chip burst facility. The most common kind of SDRAM has 168 pins. The pins are in three groups, 20, 60, 88. There is a notch between the groups. Depending on how the notches are offset, you can tell what kind of SDRAM you have. If the notch between the 20 and 60 is offset left, you have RFU (Reserved for Future Use) memory, centred: buffered, offset right: unbuffered. If the notch between the 60 and 88 is offset left, you have 5 volt memory, centred: 3.3 volt. These notches prevent you from installing the wrong kind. SDRAM DIMMs (Dual In-line Memory Modules) are now the prevailing memory architecture, edging out EDO (Extended Data Out) RAM.

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