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Ranks that share the same slot, only one rank may be accessed at any given time it is specified by activating the corresponding rank's chip select (CS) signal. Sometimes memory modules are designed with two or more independent sets of DRAM chips connected to the same address and data buses each such set is called a rank. ECC modules usually carry a multiple of 9 instead of a multiple of 8 chips. There are numerous ECC schemes, but perhaps the most common is Single Error Correct, Double Error Detect ( SECDED) which uses an extra byte per 64-bit word. Error correction ĮCC DIMMs are those that have extra data bits which can be used by the system memory controller to detect and correct errors. The SPD EEPROM connects to the System Management Bus and may also contain thermal sensors ( TS-on-DIMM). DDR4 SDRAM is neither forward nor backward compatible with any earlier type of random access memory (RAM) because of different signalling voltages, timings, as well as other differing factors between the technologies and their implementation.Ī DIMM's capacity and other operational parameters may be identified with serial presence detect (SPD), an additional chip which contains information about the module type and timing for the memory controller to be configured correctly. It is the higher-speed successor to DDR, DDR2 and DDR3.

As of August, 2014, DDR4 SDRAM is a modern emerging type of dynamic random access memory (DRAM) with a high-bandwidth ("double data rate") interface, and has been in use since 2013. 288-pin DIMM, used for DDR4 SDRAM and DDR5 SDRAM ĭDR, DDR2, DDR3, DDR4 and DDR5 all have different pin counts and/or different notch positions.278-pin DIMM, used for HP high density SDRAM.260-pin SO-DIMM, with different notch position than on DDR4 SO-DIMMs, used for UniDIMMs that can carry either DDR3 or DDR4 SDRAM.240-pin DIMM, used for DDR2 SDRAM, DDR3 SDRAM and FB-DIMM DRAM.200-pin DIMM, used for FPM/EDO DRAM in some Sun workstations and servers.200-pin SO-DIMM, used for DDR SDRAM and DDR2 SDRAM.168-pin DIMM, used for SDR SDRAM (less frequently for FPM/EDO DRAM in workstations/servers, may be 3.3 or 5 V).144-pin SO-DIMM, used for SDR SDRAM (less frequently for DDR2 SDRAM).72-pin SO-DIMM (not the same as a 72-pin SIMM), used for FPM DRAM and EDO DRAM.