RAM Types

 

EDO (Extended Data Out)

 

RAM popular in systems running 486 and Pentium I processors. Modules are called SIMM's (Single Inline Memory Modules), and must be installed in identical pairs. This type of RAM is obsolete and has not been used in systems built after 1997.

 

 

SDRAM (Synchronous Dynamic RAM)

 

The most common type of RAM, though quickly being eclipsed by newer technologies. Modules are called DIMM's (Dual Inline Memory Modules), and can be installed singly. Typically run at bus speeds of 100 MHz or 133 MHz.

 

 

DDR SDRAM (Double Data Rate SDRAM)

 

Built on SDRAM technology, but processes data at a higher rate of speed. Modules are known as DDR DIMMS and can be installed singly. Typically run at 266 MHz, but newer incarnations will run at bus speeds of 333 MHz. Typically associated with AMD Athlon CPU's, and newer Macintosh Systems

 

 

RDRAM (Rambus DRAM)

 

Considered the highest performance RAM currently available. Basic architecture is different from SDRAM and DDR SDRAM. Typically run at bus speeds of 400 MHz or higher. All memory slots on an RDRAM motherboard must be populated. Continuity RIMMS (CRIMMS) fill unused slots, but don't add RAM. RIMM's must be installed in non-contiguous pairs. Thus In one pair of slots, there will be a RIMM and an associated CRIMM. In the next bank will be a second RIMM, with its associated CRIMM. RIMM's are never installed next to each other. Associated with Pentium 4 systems, though Pentium III systems with bios updates will also support it.