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In computing, a memory module or RAM stick is a printed circuit board on which memory integrated circuits are mounted. [ 1 ] Memory modules permit easy installation and replacement in electronic systems, especially computers such as personal computers , workstations , and servers .
Some measurements of modules are size, width, speed, and latency. A memory module consists of a multiple of the memory chips to equal the desired module width. So a 32-bit SIMM module could be composed of four 8-bit wide (×8) chips. As noted in the memory channel part, one physical module can be made up of one or more logical ranks.
A DIMM (Dual In-Line Memory Module) is a popular type of memory module used in computers. It is a printed circuit board with one or both sides (front and back) holding DRAM chips and pins . [ 1 ] The vast majority of DIMMs are manufactured in compliance with JEDEC memory standards , although there are proprietary DIMMs.
The storage element of the DRAM memory cell is the capacitor labeled (4) in the diagram above. The charge stored in the capacitor degrades over time, so its value must be refreshed (read and rewritten) periodically. The nMOS transistor (3) acts as a gate to allow reading or writing when open or storing when closed. [37]
To emphasize the advantages of the DDR technique, this type of RAM was marketed at speeds twice the actual clock rate, i.e. the 400 MHz Rambus standard was named PC-800. This was significantly faster than the previous standard, PC-133 SDRAM , which operated at 133 MHz and delivered 1066 MB/s of bandwidth over a 64-bit bus using a 168-pin DIMM ...
DDR2 is a 240-pin module, DDR is a 184-pin module. Notebooks have 200-pin SO-DIMMs for DDR and DDR2; however, the notch on DDR2 modules is in a slightly different position than on DDR modules. Higher-speed DDR2 DIMMs can be mixed with lower-speed DDR2 DIMMs, although the memory controller will operate all DIMMs at same speed as the lowest-speed ...
The standards specify memory module label formats for end-user markets. [11] For example: 1GB 2Rx4 PC2-3200P-333-11-D2 is a 1 GB DDR2 Registered DIMM, with address/command parity function, using 2 ranks of x4 SDRAMs operational to PC2-3200 performance with CAS Latency = 3, tRCD = 3, tRP = 3, using JEDEC SPD revision 1.1, raw card reference ...
A test with DDR and DDR2 RAM in 2005 found that average power consumption appeared to be of the order of 1–3 W per 512 MB module; this increases with clock rate and when in use rather than idling. [14] A manufacturer has produced calculators to estimate the power used by various types of RAM. [15]