what RAM?

[STRAT]

hi guys

 

please can someone explain to me what the different types of RAM are please?

 

you now can get things like SD RAM, DDR RAM, DDRSD RAM, RD RAM etc... what is what and used where, and how do the speeds compair? it's all hurting my head a bit.

[bigcahunak]

SDRAM goes in older systems. went up to 133mhz and died arround the time P4s came out.

 

DDR=DDRSDRAM=DDRxxx the stuff that goes today. Double Data Rate SDR (SDRx2).

DDR2100 (266MHZ FSB) 2x133sdr

DDR2700 (333MHZ FSB) 2x166sdr

DDR3200 (400MHZ FSB) 2x200sdr

 

RDRAM was originally planned by Intel to be the P4s higher end system's memory, whie the older SDRAM would go in the lower end P4 rigs. Well... Intels plans failed to follow as RDRAM's price was way to high to justify the marginal increase in performance. Also, demanded more PSU power and generated more heat...

 

Bottom line - DDR is the way to go.

[Greg Hess]

Here's some bandwidth info.

 

The bandwidth of the DDR is also dependent on the bandwidth available on the front side bus. Having 400 Megahertz DDR (PC3200) doesn't do much if your running at a 200 Front Side Bus.

 

Quick Terms....

 

DDR=Double Data Rate

QDR=Quad Data Rate

 

In DDR, the chips have the ability to send data at both the peak and pits on the clock cycle. (Think of a Sin Curve), QDR [P4's FSB] has the ability to send two bits of data on both the peak and the pit.

 

Here's a great article on bandwidth, latency and such.

 

http://arstechnica.com/paedia/b/ban...-latency-1.html

 

****These are "theoretical" maximums and NOT real world maximums****

 

SDRAM

 

PC66 (66) 533 mb/sec

PC100 (100) 800 mb/sec

PC133 (133) 1.06 gb/sec

PC150 (150) 1.3 gb/sec

 

Rambus (In Dual Channel Mode)

 

PC600 (600) 2.1 gb/sec

PC700 (700) 2.8 gb/sec

PC800 (800) 3.2 gb/sec

PC1066 (1066) 4.3 gb/sec

 

DDR

 

PC1600 (200) 1.6 gb/sec

PC2100 (266) 2.1 gb/sec

PC2700 (333) 2.7 gb/sec

PC3200 (400) 3.2 gb/sec

PC3500 (440) 3.5 gb/sec

 

DCDDR (Dual Channel DDR)

 

PC2100 (266) 4.2 gb/sec

PC2700 (333) 5.4 gb/sec

PC3200 (400) 6.4 gb/sec

 

100/133 FSB

 

100 800 mb/sec

133 1.06 gb/sec

 

Athlon EV6 Bus (DDR)

 

200 1.6 gb/sec

266 2.1 gb/sec

333 2.7 gb/sec

 

Pentium IV QDR Bus

 

400 3.2 gb/sec

533 4.3 gb/sec

800 6.4 gb/sec

 

Its interesting to note how the DDR400 (PC3200 DCDDR) fits perfectly with intel's recently announced 800 FSB. Rambus couldn't even begin to touch upon that much bandwidth, so its easy to see why intel completely abandoned that particular memory technology.