本文主要介绍Memory Module的种类、标准等。
常见的一些Memory Module类型如下：
DIMM：Dual In-line Memory Module
UDIMM：Unbuffered DIMM
UniDIMM：Universal DIMM
RDIMM：Registered DIMM
USODIMM：Unbuffered SO-DIMM
RDIMM：Registered DIMM
LRDIMM：Load Reduced DIMM
SODIMM：Small Outline DIMM
FB-DIMM：Fully Buffered DIMM
MicroDIMM
Unbuffered MicroDIMM
MiniDIMM
Registered MiniDIMM
RIMM：Rambus In-line Memory Module
SO-RIMM：Small outline RIMM
SIMM：Single In-line Memory Module
NVDIMM：Non-Volatile DIMM
其中NVDIMM又分为如下两种：JEDEC Standard和Non-Standard NVDIMM。
There are three types of NVDIMM implementations by JEDEC Standards org：
NVDIMM-F: DIMM with flash storage. System users will need to pairthe storage DIMM along side a traditional DRAM DIMM. NVDIMM-F has beenavailable since 2014.
NVDIMM-N: DIMM with flash storage and traditional DRAM on the samemodule. The computer accesses the traditional DRAM directly. In the event of apower failure, the module copies the data from the volatile traditional DRAM tothe persistent flash storage, and copies it back when power is restored. Ituses a small backup power source for this.
NVDIMM-P: specifications will be released by JEDEC around 2018 Itwill allow storage inside computer main memory, using ReRAM technology, and aDDR5 interface. A NVDIMM-P has persistent DRAM, and can access externalblock-oriented (flash memory) drive for memory cache.
and one Non-Standard NVDIMM implementations： NVDIMM-X：DDR4 DIMM with NAND Flash storageand volatile DRAM on the same module, developed by Xitore.
每一种类型的module都有其各自的接口形态，详细如下：
30-pin SIMMs, usually FPRAM
72-pin SIMMs, often extended data out DRAM(EDO DRAM) but FPRAM is not uncommon
72-pin SO-DIMM (not the same as a 72-pinSIMM), used for FPM DRAM and EDO DRAM
100-pin DIMM, used for printer SDRAM
100-pin SO-DIMM, used for SDR SDRAM
144-pin SO-DIMM, used for SDR SDRAM (lessfrequently for DDR2 SDRAM)
168-pin DIMM, used for SDR SDRAM (lessfrequently for FPM/EDO DRAM in workstations/servers, may be 3.3 or 5 V)
172-pin MicroDIMM, used for DDR SDRAM
184-pin DIMM, used for DDR SDRAM
184-pin RIMM (Rambus in-line memory module)form factor, similar to a DIMM (dual in-line memory module). Data istransferred on both the rising and falling edges of the clock signal, atechnique known as DDR. To emphasize the advantages of the DDR technique, thistype of RAM was marketed at speeds twice the actual clock rate, i.e. the 400MHz Rambus standard was named PC-800. This was significantly faster than theprevious standard, PC-133 SDRAM, which operated at 133 MHz and delivered 1066MB/s of bandwidth over a 64-bit bus using a 168-pin DIMM form factor.
200-pin SO-DIMM, used for DDR SDRAM andDDR2 SDRAM
200-pin DIMM, used for FPM/EDO DRAM in someSun workstations and servers.
204-pin SO-DIMM, used for DDR3 SDRAM
214-pin MicroDIMM, used for DDR2 SDRAM
240-pin DIMM, used for DDR2 SDRAM, DDR3SDRAM and FB-DIMM DRAM
240-pin DDR2 FB-DIMMs are neithermechanically nor electrically compatible with conventional 240-pin DDR2 DIMMs.
244-pin MiniDIMM, used for DDR2 SDRAM
260-pin SO-DIMM, used for DDR4 SDRAM
260-pin SO-DIMM, with different notchposition than on DDR4 SO-DIMMs, used for UniDIMMs that can carry either DDR3 orDDR4 SDRAM
260-pin UniDIMMs, which has the same pincount as the one on DDR4 SO-DIMMs, with the keying notch in a position thatprevents incompatible installation by making UniDIMMs physically incompatiblewith standard DDR3 and DDR4 SO-DIMM sockets.
278-pin DIMM, used for HP high densitySDRAM.
288-pin DIMM, used for DDR4 SDRAM
针对每一种module的接口形态，JEDEC都有其相关标准，分类如下：
JC-45.1: Registered DRAM Modules
JC-45.3: Unbuffered DRAM Modules
JC-45.4: Fully Buffered DRAM Modules
JC-45.5: Module Interconnect
JC-45.6: Hybrid Modules
其中主要的是MODULE4.20，详细如下：
4.20.2 - 168-Pin, PC133 SDRAM Registered DIMM Design Specification
4.20.3 - 144-Pin, PC133 SDRAM Unbuffered SO-DIMM, Reference DesignSpecification
4.20.4 - 184-Pin, PC1600/2100 DDR SDRAM Registered DIMM DesignSpecification
4.20.5 - 184-Pin, PC1600/2100 DDR SDRAM Unbuffered DIMM Design Specification
4.20.6 - 200-Pin, PC3200/PC2700 DDR SDRAM Unbuffered SO-DIMM ReferenceDesign Specification
4.20.7- 184-Pin, PC2700/3200 DDR SDRAM Registered DIMM ReferenceDesign Specification
4.20.8- 184-Pin, PC3200/PC2700 DDR SDRAM Unbuffered DIMM withTSOP-Based DRAMs Reference Design Specification
4.20.9- 100-Pin, DDR SDRAM Unbuffered 32b DIMM Reference DesignSpecification
4.20.10- 240-Pin, PC2-6400/PC2-5300/PC2-4200/PC2-3200 DDR2 SDRAMRegistered DIMM Reference Design Specification
4.20.11- 200-Pin, PC2-6400/PC2-5300/PC2-4200/PC2-3200 DDR2 SDRAMUnbuffered SO-DIMM Reference Design Specification
4.20.12- 214-Pin, PC2-4200/PC2-3200 DDR2 SDRAM Unbuffered MicroDIMMReference Design Specification
4.20.13- 240-Pin, PC2-5300/PC2-6400 DDR2 SDRAM Unbuffered DIMMReference Design Specification
4.20.14- 244-Pin, PC2-4200/PC2-3200 DDR2 SDRAM Registered Mini-DIMMReference Design Specification
4.20.15- 240-Pin, PC2-4200/PC2-5300/PC2-6400 DDR2 SDRAM FullyBuffered DIMM Reference Design Specification
4.20.16- 144-Pin, EP2-2100 DDR2 SDRAM 32b-SO-DIMM Reference Design Specification
4.20.17- 240-Pin, 214-Pin PC3-12800 DDR3 Unbuffered MicroDIMM Reference Design Specification
4.20.18- 204-Pin, PC3-6400/PC3-8500/PC3-10600/PC3-12800 DDR3Unbuffered SO-DIMM Reference Design Specification
4.20.19- 240-Pin, PC3-6400/PC3-8500/PC3-10600/PC3-12800 DDR3Unbuffered DIMM Reference Design Specification
4.20.20- 240-Pin, PC3-6400/PC3-8500/PC3-10600/PC3-12800 DDR3Registered DIMM Reference Design Specification
4.20.21- 204-Pin, EP3-6400/EP3-8500/EP3-10600/EP3-12800 DDR3 SDRAM 72b-SO-DIMMReference Design Specification
4.20.22- 144-Pin DDR3 SDRAM Unbuffered 32b-SO-DIMM DesignSpecification
4.20.23- 240-Pin, 72 bit-wide, PC3-6400/PC3-8500/PC3-10600/PC3-12800/PC3-14900/PC3-17000 DDR3 SDRAM RegisteredDIMM Design Specification
4.20.24- 240-Pin, 72 bit-wide, PC3(L)-6400/PC3(L)-8500/PC3(L)-10600/PC3(L)-12800/PC3(L)-14900/PC3(L)-17000DDR3 SDRAM Load Reduced DIMM Design Specification
4.20.25- 260-Pin, 1.2 V (VDD), PC4-1600/PC4-1866/PC4-2133/PC4-2400/PC4-2666/PC4-3200 DDR4 SDRAM SO-DIMM DesignSpecification
4.20.26- 288-Pin, 1.2 V (VDD), PC4-1600/PC4-1866/PC4-2133/PC4-2400/PC4-2666/PC4-3200 DDR4 SDRAM UnbufferedDIMM Design Specification
4.20.27- 288-Pin, 1.2 V (VDD), PC4-1600/PC4-1866/PC4-2133/PC4-2400/PC4-2666/PC4-3200 DDR4 SDRAM Load ReducedDIMM Design Specification
4.20.28- 288-Pin, 1.2 V (VDD), PC4-1600/PC4-1866/PC4-2133/PC4-2400/PC4-2666/PC4-3200 DDR4 SDRAM RegisteredDIMM Design Specification
几种常见的DIMM的简单区别如下：
从价格的角度看，RDIMM比较适中。小容量的UDIMM较为便宜，但是由于制造工艺要求高，大容量的UDIMM价格甚至超过RDIMM。LRDIMM价格高于RDIMM与UDIMM。
从容量的角度看，只有LRDIMM能够支持到最大化的总内存容量。不过主要应用所需要的内存容量一般通过部署RDIMM就可以达到。
从主频的角度看，目前RDIMM支持的频率较高，可以拥有更大的带宽和小时延。
从时延的角度看，虽然同频率下UDIMM时延最小，但是RDIMM可以支持1.6GHz，用更高的频率来降低时延。
从功耗的角度看，LRDIMM最高，RDIMM和UDIMM较低。
如果需要最大的内存容量，就必须使用LRDIMM；如果不需要最大的内存容量，使用RDIMM（1.6GHz）性能、价格和可扩展性较好；如果考虑功耗，可以使用低功耗LP内存，并控制其运行在较低频率下。
以上就是针对Memory Module的一些简单的介绍，详细可参见JEDEC的相关标准。
