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Recognizing DDR Memory Modules Part-3


Wednesday, May 23, 2001 Part-3

Identifying DIMM Module by Label

JEDEC has also issued a standard for labeling the DDR DIMM module. A standard DDR DIMM module should have at least one label on the module. The label should contain the following information:



Where:
“wwww” = Module Bandwidth
1600: 1.6GB/sec or 2100: 2.1GB/sec.

“m” = Module Type
R= Registered DIMM
U= Unbuffered DIMM (no register on DIMM)

“aa” = SDRAM CAS Latency, with no decimal point (25=2.5ns CAS Latency)

“b” = SDRAM minimum tRCD specification (in clocks)

“c” = SDRAM minimum tRP specification (in clocks)

“d” = JEDEC SPD Revision used on this DIMM

“e” = Gerber file used for this design (if applicable)
A= Reference design of R/C ‘A’ is used for this assembly
B= Reference design of R/C ‘B’ is used for this assembly
C= Reference design of R/C ‘C’ is used for this assembly
D= Reference design of R/C ‘D’ is used for this assembly
E= Reference design of R/C ‘E’ is used for this assembly
F= Reference design of R/C ‘F’ is used for this assembly
H= Reference design of R/C ‘H’ is used for this assembly
K= Reference design of R/C ‘K’ is used for this assembly
Z= Reference design of R/C ‘Z’ is used for this assembly

“f” = Revision number of the reference design used:
1 = 1st revision ( 1st release)
2 = 2nd revision (2nd release)
3 = 3rd revision (3rd release)
Bank= Not Applicable (used with ‘Z’ above)

Example: PC1600R-25330-A1
Is a PC1600 DDR Registered DIMM with CL=2.5, tRCD=3, tRP=3
Using the latest JEDEC SPD Revision 0.0 and produced based on the “A” raw card Gerber, 1st release.


A Note on Module Bandwidth
In theory, higher memory bandwidth will deliver better performance for the computer system. Memory peak bandwidth is defined as memory bus width/8 bits x data rate.

That translates into how fast your 3D games will react, how smooth your MP3 music will play or how good a motion picture you can play in your MPEG video streaming. Bandwidth calculation: memory bus width/8 bits x data rate.

For example: memory bus width for the 184pin DDR module is 64bits, data rate of the DDR SDRAM is usually 266MHz. That makes the peak bandwidth = 64/8X266MHz = 2100MHz.


Click here to find out more about Part-4



By: DocMemory
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