Two types of DIMMs: a 168-pin SDRAM module (top) and a 184-pin DDR SDRAM module (bottom). The SDRAM module has two notches (rectangular cuts or incisions) on the bottom edge, while the DDR1 SDRAM module has only one. Also, each module has eight RAM chips, but the lower one has an unoccupied space for the ninth chip; this space is occupied in ECC DIMMs

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Ddr4 So Dimm

Three SDRAM DIMM slots on a computer motherboard

Installing SO-DIMM-Modules into mobile devices/laptops. Hold the SO-DIMM-module by the sides and slide it into the correct slot at the appropriate angle, golden contacts first. Insert the module carefully until you can no longer see the golden contacts and the module is snug in its slot. The 8GB DIMM RAM means it has a slot (or more) where you can plug a RAM module in. DIMM stands for Dual In-line Memory Module. That’s an industry standard. For notebooks it’s called SO-DIMM (essentially the same but points out specifically that this slot using the smaller RAM module you usually associate to plug into a notebook). Installing SO-DIMM-Modules into mobile devices/laptops. Hold the SO-DIMM-module by the sides and slide it into the correct slot at the appropriate angle, golden contacts first. Insert the module carefully until you can no longer see the golden contacts and the module is snug in its slot. Jetway JNF9QU-Q87 Intel Socket LGA 1150, HDMI, 4.SATA3 + mSATA/mPCIE Combo, Onboard TPM, Mini-ITX MB. Memory Standard: DDR3 1600 Number of Memory Slots: 2×204pin SO-DIMM Audio Chipset: Realtek ALC662.

A DIMM or dual in-line memory module, commonly called a RAM stick, comprises a series of dynamic random-access memoryintegrated circuits. These modules are mounted on a printed circuit board and designed for use in personal computers, workstations and servers. DIMMs began to replace SIMMs (single in-line memory modules) as the predominant type of memory module as IntelP5-based Pentium processors began to gain market share.

While the contacts on SIMMs on both sides are redundant, DIMMs have separate electrical contacts on each side of the module. Another difference is that standard SIMMs have a 32-bit data path, while standard DIMMs have a 64-bit data path. Since Intel's Pentium, many processors have a 64-bit bus width, requiring SIMMs installed in matched pairs in order to populate the data bus. The processor would then access the two SIMMs in parallel. DIMMs were introduced to eliminate this disadvantage.

Variants[edit]

Variants of DIMM slots support DDR, DDR2, DDR3, DDR4 and DDR5 RAM.

Common types of DIMMs include the following:

SDRAM	SDR SDRAM	DDR SDRAM	DDR2 SDRAM	DDR3 SDRAM	DDR4 SDRAM	DDR5 SDRAM	FPM DRAM and EDO DRAM	FB-DIMM DRAM
DIMM	100-pin	168-pin	184-pin	240-pin^[a]		288-pin^[a]		168-pin	240-pin
SO-DIMM	N/A	144-pin	200-pin^[a]		204-pin	260-pin	72-pin/144-pin	N/A
MicroDIMM	N/A	144-pin	172-pin	214-pin	N/A			N/A

70 to 200 pins

72-pin SO-DIMM (not the same as a 72-pin SIMM), used for FPM DRAM and EDO DRAM
100-pin DIMM, used for printer SDRAM
144-pin SO-DIMM, used for SDR SDRAM (less frequently for 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)
172-pin MicroDIMM, used for DDR SDRAM
184-pin DIMM, used for DDR SDRAM
200-pin SO-DIMM, used for DDR SDRAM and DDR2 SDRAM
200-pin DIMM, used for FPM/EDO DRAM in some Sun workstations and servers.

201 to 300 pins

204-pin SO-DIMM, used for DDR3 SDRAM
214-pin MicroDIMM, used for DDR2 SDRAM
240-pin DIMM, used for DDR2 SDRAM, DDR3 SDRAM and FB-DIMM DRAM
244-pin MiniDIMM, used for DDR2 SDRAM
260-pin SO-DIMM, used for DDR4 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
278-pin DIMM, used for HP high density SDRAM.
288-pin DIMM, used for DDR4 SDRAM and DDR5 SDRAM^[1]

168-pin SDRAM[edit]

Notch positions on DDR (top) and DDR2 (bottom) DIMM modules

On the bottom edge of 168-pin DIMMs there are two notches, and the location of each notch determines a particular feature of the module. The first notch is the DRAM key position, which represents RFU (reserved future use), registered, and unbuffered DIMM types (left, middle and right position, respectively). The second notch is the voltage key position, which represents 5.0 V, 3.3 V, and RFU DIMM types (order is the same as above).

DDR DIMMs[edit]

8 GB DDR4-2133 ECC 1.2 V RDIMMs

DDR, DDR2, DDR3, DDR4 and DDR5 all have different pin counts and/or different notch positions. 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. It is the higher-speed successor to DDR, DDR2 and DDR3. 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.

SPD EEPROM[edit]

A 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. The SPD EEPROM connects to the System Management Bus and may also contain thermal sensors (TS-on-DIMM).^[2]

Error correction[edit]

ECC DIMMs are those that have extra data bits which can be used by the system memory controller to detect and correct errors. 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. ECC modules usually carry a multiple of 9 instead of a multiple of 8 chips.

Ranking[edit]

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. 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. The other ranks on the module are deactivated for the duration of the operation by having their corresponding CS signals deactivated. DIMMs are currently being commonly manufactured with up to four ranks per module. Consumer DIMM vendors have recently begun to distinguish between single and dual ranked DIMMs.

After a memory word is fetched, the memory is typically inaccessible for an extended period of time while the sense amplifiers are charged for access of the next cell. By interleaving the memory (e.g. cells 0, 4, 8, etc. are stored together in one rank), sequential memory accesses can be performed more rapidly because sense amplifiers have 3 cycles of idle time for recharging, between accesses.

DIMMs are often referred to as 'single-sided' or 'double-sided' to describe whether the DRAM chips are located on one or both sides of the module's printed circuit board (PCB). However, these terms may cause confusion, as the physical layout of the chips does not necessarily relate to how they are logically organized or accessed.

JEDEC decided that the terms 'dual-sided', 'double-sided', or 'dual-banked' were not correct when applied to registered DIMMs (RDIMMs).

Organization[edit]

Most DIMMs are built using '×4' ('by four') or '×8' ('by eight') memory chips with nine chips per side; '×4' and '×8' refer to the data width of the DRAM chips in bits.

In the case of '×4' registered DIMMs, the data width per side is 36 bits; therefore, the memory controller (which requires 72 bits) needs to address both sides at the same time to read or write the data it needs. In this case, the two-sided module is single-ranked. For '×8' registered DIMMs, each side is 72 bits wide, so the memory controller o

So-dimm Slots