35781 Slajd17 (112)

FPM was the traditional RAM for PCs, before the EDO was mtroduced. It is mounted in SIMM modules of 2, 4, 8, 16, or 32 MB. Typically, it is found in 60 ns or 70 ns versions. 60 ns is the fastest and the one to use. You cannot mix different speeds on the same Pentium motherboard.

EDO (Extended Data Out) RAM is an improvement of FPM RAM. Data are read faster. EDO extends the time that output data is valid, which betters timing issues between the CPU and RAM and this way improves the performance.

By switching from FPM to EDO, one could expect a performance improvement of 2 to 5 percent. EDO RAM was usually sold in 60 ns versions. A 50 ns version was available at higher cost.

EDO has now been replaced by the even faster SDRAM.

ECC RAM is a special error correcting RAM type. It is espeaally used in servers.

SDRAM (synchronous DRAM)): The replacement for DRAM, FPM, and EDO RAM types. SDRAM "locks" (synchronizes) the memory access to the CPU clock. This way we get faster data transfer. While one portion of data is tranported to the CPU another can be being prepared for transfer.

SDRAM comes only in 64 bit modules (long 168 pin DIMMs). SDRAM has a access time of only 6-12 ns. The performance improvement over EDO RAM was a mere 5 percent running at 66 MHz. At 100 and 133 MHz it proves better.

DDR RAM is clock doubled version of SDRAM, which is replacing SDRAM during 2001-2002.

RAMBUS (RDRAM) is a morę futuristic RAM type. Intel and others had great expectations from this type, but it flopped in 2000-2001.