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Wednesday, April 16, 2014
Memory Articles and Publications
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Recognizing DDR Memory Modules Part-2


Wednesday, May 23, 2001

Part-2
Steps in Identifying a DDR Memory Module

One of the easiest and most basic step in identifing a DDR memory module is by the Physical Shape.

In order to guaranty performance of DDR module in the computer systems, JEDEC has asked all memory module producers to adhere to the example DIMM module PCB designs done by two JEDEC member companies.

These example designs are opened to the public through the IBM and the Micron technology enabling Web sites. The two sites are :

184pin Registered DDR DIMM – hosted by IBM Micro-electronics
Click Here for IBM

184pin Unbuffered DDR DIMM – hosted by Micron Technology
Click here for Micron

A Note on Registered and Unbuffered Modules:
Consumer class of personal computer usually have 2 to 3 DIMM sockets and is for limited amount of memory only. The electrical loading on these 2 to 3 modules are usually tolerated by the motherboard with some compromise on performance. The memory module they use in this case is called Unbuffered DIMM which is cost optimized for the consumer applications. On the contrary, server class of personal computer must have huge amount of memory with high performance. Up to 8 DIMM sockets are usually designed into a server. In this case, signal buffering and timing lineup is necessary to keep the integrity on the high-speed memory access signals. A signal shaping circuit including registers and phase-lock-loops are required to be on the DIMM module. This kind of module is called the Registered DIMM.

Each of the above Web sites had included 3 available DIMM PCB designs they named as RawCard A, B and C. They are the DIMM PCB designs presented in a commonly acceptable format called “Gerber”. With these sets of “Gerber” files, any memory producer can produce PC boards in uniform nature.

Diagram of Registered RawCard A , single Bank x 64



Diagram of Registered RawCard A , single Bank ECC



Diagram of Registered RawCard A , Two Bank x 64



Diagram of Registered RawCard A , Two Bank ECC



Diagram of Registered RawCard B



Diagram of Registered RawCard C



Diagram of Unbuffered RawCard A Single Bank x 64



Diagram of Unbuffered RawCard A Single bank ECC



Diagram of Unbuffered RawCard B Two Bank x 64



Diagram of Unbuffered RawCard B Two bank ECC



Diagram of Unbuffered RawCard C Two Bank x 64



Diagram of Unbuffered RawCard C Two bank ECC



DDR DIMM is also characterized by the 184pin count and a single socket registration notch in the middle of the gold finger contacts.

Click here to find out more about Part-3




















By: DocMemory
Copyright © 2001 CST, Inc. All Rights Reserved

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