Types of RAM: How to Identify and their Specifications

There are many different types of RAM which have appeared over the years and it is often difficult knowing the difference between them both performance wise and visually identifying them. This article tells a little about each RAM type, what it looks like and how it performs.

FPM RAM
FPM RAM, which stands for “Fast Page Mode RAMÃ is a type of Dynamic RAM (DRAM). The term "Fast Page Mode" comes from the capability of memory being able to access data that is on the same page and can be done with less latency. Most 486 and Pentium based systems from 1995 and earlier use FPM Memory.


EDO RAM
EDO RAM, which stands for "Extended Data Out RAM" came out in 1995 as a new type of memory available for Pentium based systems. EDO is a modified form of FPM RAM which is commonly referred to as "Hyper Page Mode". Extended Data Out refers to fact that the data output drivers on the memory module are not switched off when the memory controller removes the column address to begin the next cycle, unlike FPM RAM. Most early Penitum based systems use EDO.


SDRAM
SDRAM , which is short for Synchronous DRAM is a type of DRAM that runs in synchronization with the memory bus. Beginning in 1996 most Intel based chipsets began to support SDRAM which made it a popular choice for new systems in 2001.
SDRAM is capable of running at 133MHz which is about three times faster than FPM RAM and twice as fast as EDO RAM. Most Pentium or Celeron systems purchased in 1999 have SDRAM.


DDR RAM
DDR RAM, which stands for "Double Data Rate" which is a type of SDRAM and appeared first on the market around 2001 but didn’t catch on until about 2001 when the mainstream motherboards started supporting it. The difference between SDRAM and DDR RAM is that instead of doubling the clock rate it transfers data twice per clock cycle which effectively doubles the data rate. DDRRAM has become mainstream in the graphics card market and has become the memory standard.


DDR2 RAM
DDR2 RAM, which stands for "Double Data Rate 2" is a newer version of DDR which is twice as fast as the original DDR RAM. DDR2RAM came out in mid 2003 and the first chipsets that supported DDR2 came out in mid 2004. DDR2 still is double data rate just like the original DDR however DDR2-RAM has modified signaling which enables higher speeds to be achieved with more immunity to signal noise and cross-talk between signals.


RAMBUS (RIMM) RAM
RAMBUS RDRAM is a type of ram of its own, it came out in 1999 and was developed from traditional DRAM but its architecture is totally new. The RAMBUS design gives smarter access to the ram meaning that units can prefetch data and free some CPU work. The idea behind RAMBUS RAM is to get small packets of data from the RAM, but at very high clock speeds. For example, SD RAM can get 64bit of information at 100MHz where RAMBUS RAM would get 16bits of data at 800MHz. RIMM ram was generally unsuccessful as Intel had a lot of problems with the RAM timing or signal noise. RD RAM did make an appearance in the Sony Playstation 2 and the Nintendo 64 game consoles.


Memory Module and Bus Standards/Bandwith

Module Standard	Module Format	Chip Type	Clock Speed (MHz)	Cycles per Clock	Bus Speed (MT/s)	Bus Width (Bytes)	Transfer Rate (MBps)
FPM	SIMM	60ns	22	1	22	8	177
EDO	SIMM	60ns	33	1	33	8	266
PC66	SDR DIMM	10ns	66	1	66	8	533
PC100	SDR DIMM	8ns	100	1	100	8	800
PC133	SDR DIMM	7/7.5ns	133	1	133	8	1,066
PC1600	DDR DIMM	DDR200	100	2	200	8	1,600
PC2100	DDR DIMM	DDR266	133	2	266	8	2,133
PC2400	DDR DIMM	DDR300	150	2	300	8	2,400
PC2700	DDR DIMM	DDR333	166	2	333	8	2,667
PC3000	DDR DIMM	DDR366	183	2	366	8	2,933
PC3200	DDR DIMM	DDR400	200	2	400	8	3,200
PC3500	DDR DIMM	DDR433	216	2	433	8	3,466
PC3700	DDR DIMM	DDR466	233	2	466	8	3,733
PC4000	DDR DIMM	DDR500	250	2	500	8	4,000
PC4200	DDR DIMM	DDR533	266	2	533	8	4,266
PC2-3200	DDR2 DIMM	DDR2-400	200	2	400	8	3,200
PC2-4200	DDR2 DIMM	DDR2-533	266	2	533	8	4,266
PC2-5300	DDR2 DIMM	DDR2-667	333	2	667	8	5,333
PC2-6000	DDR2 DIMM	DDR2-750	375	2	750	8	6,000
PC2-6400	DDR2 DIMM	DDR2-800	400	2	800	8	6,400
PC2-7200	DDR2 DIMM	DDR2-900	450	2	900	8	7,200
PC2-8000	DDR2 DIMM	DDR2-1000	500	2	1000	8	8,000
RIMM1200	RIMM-16	PC600	300	2	600	2	1,200
RIMM1400	RIMM-16	PC700	350	2	700	2	1,400
RIMM1600	RIMM-16	PC800	400	2	800	2	1,600
RIMM2100	RIMM-16	PC1066	533	2	1066	2	2,133
RIMM2400	RIMM-16	PC1200	600	2	1200	2	2,400
RIMM3200	RIMM-32	PC800	400	2	800	4	3,200
RIMM4200	RIMM-32	PC1066	533	2	1066	4	4,266
RIMM4800	RIMM-32	PC1200	600	2	1200	4	4,800