• Dimm Memory Module
• Ddr Memory Type
• Dimm Types
• Dimm Pins

1 DIMM means that the RAM occupies one of the two slots on the notebook. 2 DIMMs means that the RAM occupies both of the slots of the notebook. So if you ordered 1GB of RAM, it would be 1x1GB in a 1 DIMM configuration or 2x512MB in a 2 DIMM configuration.

1. Basically, it is a type of Random Access Memory (RAM) slot, that supports Double Data Rate (DDR) RAM. DDR RAM is said to be twice as fast as Synchronous Dynamic (SD) RAM.
2. DDR3 is a type of SDRAM that is used for system memory. It is available in both DIMM and SO-DIMM form factors. DDR3 RAM is similar to DDR2 RAM, but uses roughly 30% less power and can transfer data twice as fast.

Terminology[edit]

Hi. Thanks for the explanation. I still don't understand what is 'dual' about the dim, nor do I understand what is 'in line' about it. Is the DIMM 'dual' because it carries information on each side of a pin? I am trying to understand what makes a DIMM, different than a SIMM. Thanks for any help you can provide.—Preceding unsigned comment added by 138.88.66.226 (talk • contribs) 0:20 UTC, 14 February 2005

the major difference between simm and dimm is that simm can work on single line that is it can work on one side of the ram whereas dimm which is dual in line memory module can work on both sides of the ram.

sub:varun verma —Preceding unsigned comment added by 202.164.55.50 (talk • contribs) 08:30 UTC, 20 June 2005

hello my name is siby. i whish you include the speed of DIMM used in computer system.

I added an explination of the differences between DIMMs and SIMMs. And I think this article has enough information that we can remove the stub status. Any objections? --Pboyd04 20:42, 26 December 2005 (UTC)

Pin layout[edit]

Does anyone have references for the pin layouts and method of operation of the different types of DIMM?It would certainly be useful to address this topics. JulesH 11:17, 13 October 2006 (UTC)

you 're right. i have inserte the package gorm of 168 pin (13 cm and 2 holes), i'd like to see others version too. --83.190.155.53 17:10, 12 September 2007 (UTC)

ps i was looking for package list and i found this page [1] (sorry this is a commercial site but i haven't found a free site yet) —Preceding unsigned comment added by 83.190.155.53 (talk) 17:16, 12 September 2007 (UTC)

As far as I know DIMM SDRAM memory has 184pinn,and one hole in the center.The 2 holes might be DDR SDRAM. —Preceding unsigned comment added by 71.206.65.120 (talk) 22:21, 27 March 2009 (UTC)

DDR1 and DDR2 Speed[edit]

In the speed section can you clarify the difference between the speeds of DDR1 and DD2... is the strobe at the same speed as the data and twice the clock in both cases? ...

DDR1 ...have data but not the strobe at double the rate of the clock. i.e., PC1600 = 200 MHz data & strobe / 100 MHz clock for address and control ....DDR2 ... also (?) have data and data strobe frequencies at double the rate of the clock. i.e., PC2-3200 = 400 MHz data & strobe / 200 MHz clock for address and control ....Jnwisner 16:45, 14 July 2007 (UTC)

Memory module description in EEPROM chip[edit]

I miss a notice that most DIMM modules carry a small EEPROM chip that describeS specification of the module (capacity, timing, manufacturer, etc). And I miss a detail article about this EEPROM chip, that is accesible at I2C bus on most cases as I know. Information from the chip can be read with Z-CPU freeware under Windows, for example. BIOS process the information from EEPROM chip too to configure system to optimal values during computer boot.

Well, I found the article about SPD: Serial_Presence_Detect—Preceding unsigned comment added by 89.24.36.147 (talk) 11:12, 27 January 2008 (UTC)

Am I wrong or is this whole section plain wrong?There's DIMM SDRAM,and DDR SDRAM; a big difference!It seems they mix it up a bit!DIMM SDRAM = supposed to be 184 pin, one hole on the bottom, 2 holes on the sides, and speeds ranging somewhere like 66 to 100Mhz. (It might be possible that 33Mhz or 133Mhz exists too).DDR speeds usually go higher then 100Mhz. —Preceding unsigned comment added by 71.206.65.120 (talk) 22:24, 27 March 2009 (UTC)

MicroDIMM?[edit]

Given that there's no definition of exactly what a MicroDIMM is, in what devices it is used, etc., I have a hard time understanding why MicroDIMM redirects here, other than the fact that the word is on the page. Anyone care to add a description? —Preceding unsigned comment added by 67.91.44.34 (talk) 15:53, 6 March 2008 (UTC)

My laptop has a MicroDimm slot fare as i know its used for more memory all u know at the moment but will keep u informed if i find out much more :)J M F Daddy

Other DIMMs than mainstream?[edit]

What about DIMMs used e.g. in printers, set-top boxes, cisco router, etc. pp.? Not even mentioned here... I don't have any information about them but they occur mostly in powerpc appliances and areequipped with sdrams as well as with normal drams. —Preceding unsigned comment added by 79.196.219.73 (talk) 19:39, 22 June 2009 (UTC)

Yes, other DIMMs[edit]

I worked as atech for Computer City and ran into regular sized 144-pin DIMMs several times. They were basically mirrored 72-pin SIMMs, if you put them into the computer only half the RAM is available. I remember Canon desktop computers used those and the memory slots could interchange 72 and 144 pin variants. There was another brand, I think it was UMAX MAC clone (at that short time that Apple was licensing their OS). Apple had eprom DIMMs for Mac ROMs. Shjacks45 (talk) 20:02, 16 March 2012 (UTC)

Ease of installation comparison[edit]

Add a comparison table of ease of installation, e.g., in http://www.wikihow.com/Install-RAM

Press gently but firmly until the clamps close completely. You may need to push the clamps in toward the chip, but do so very gently. If the chip does not fit, do not force it.

Perhaps other designs are easier for the user.... Jidanni (talk) 02:16, 17 July 2012 (UTC)

The description for DDR3 and DDR4 is basically the same.[edit]

I'm no expert, but this seems weird. Surely it should be quadruple the clock speed, and not just double? I don't feel certain enough to edit, but if someone else knows anything about it this should at least be clarified. — Preceding unsigned comment added by 192.76.8.18 (talk) 12:22, 25 August 25 2014‎ (UTC)

Hello! Actually, DDR(1), DDR2, DDR3 and DDR4 all perform at double the rate of their clocks. The n in DDRn serves as a generation designation. — Dsimic (talk | contribs) 03:44, 26 August 2014 (UTC)

Registered DIMMs[edit]

The term/concept 'registered DIMM' is used and not explained.

'JEDEC decided that the terms 'dual-sided,' 'double-sided,' or 'dual-banked' were not correct when applied to registered DIMMs.'84.55.110.220 (talk) 08:55, 10 March 2015 (UTC)

Hello! Please see the DIMM § 168-pin SDRAM section above – it contains a link to the Registered memory article, which explains the whole concept. In Wikipedia articles, it is a common practice not to link the same term multiple times, so 'registered' isn't linked more than once. — Dsimic (talk | contribs) 10:18, 10 March 2015 (UTC)

Concerning section: 168-pin SDRAM[edit]

I don't know if it's me, but I can only see one notch on the bottom edge...

Also, just to clarify, the notch is the thing that makes it impossible to but it in the wrong way or to put in a module not designed for the slot at all, right? — Preceding unsigned comment added by 84.55.110.220 (talk) 09:06, 10 March 2015 (UTC)

Please make sure you're looking at the right image; File:DIMMs.jpg (which is visible at the top of the article) shows a 168-pin SDRAM DIMM, which clearly has two notches. You're right, the notch is the mechanical characteristic of a DIMM module's edge connector that makes it impossible to mismatch memory types. — Dsimic (talk | contribs) 10:24, 10 March 2015 (UTC)

definition - DIMM

definition of Wikipedia

phrases

Fully Buffered DIMM • SO-DIMM

Wikipedia

A DIMM or dual in-line memory module, 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.

Dimm Memory Module

The main difference between SIMMs and DIMMs is that DIMMs have separate electrical contacts on each side of the module, while the contacts on SIMMs on both sides are redundant. 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 has (as do several other processors) a 64-bit bus width, it requires SIMMs installed in matched pairs in order to complete the data bus. The processor would then access the two SIMMs simultaneously. DIMMs were introduced to eliminate this practice.

The most common types of DIMMs are:

• 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
• 168-pin DIMM, used for SDR SDRAM (less frequently for FPM/EDO DRAM in workstations/servers)
• 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
• 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

Ddr Memory Type

168-pin SDRAM

On the bottom edge of 168-pin DIMMs there are 2 notches, and the location of each notch determines a particular feature of the module.

• The first notch is DRAM key position. It represents RFU (reserved future use), registered, and unbuffered (in that order from left to middle to right position).
• The second notch is voltage key position. It represents 5.0V, 3.3V, and Reserved (order as above).
• The upper DIMM in the (topmost) photo is an unbuffered 3.3V 168-pin DIMM. DIMM slots support also DDR1, 2, 3 RAM.

DDR DIMMs

DDR, DDR2 and DDR3 all have a different pin-counts, and different notch positions.

SPD EEPROM

A DIMM's capacity and timing 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.

Dimm Types

Error correction

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

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. Since all ranks share the same buses, only one rank may be accessed at any given time; it is specified by activating the corresponding rank's chip select (CS) signal. All other ranks 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.

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.

Organization

Dimm Pins

Most DIMMs are built using '×4' (by 4) memory chips or '×8' (by 8) memory chips with 9 chips per side. '×4' or '×8' refer to the data width of the DRAM chips in bits.

In the case of the '×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 only addresses one side at a time (the two-sided module is dual-ranked).

Speeds

For various technologies, there are certain bus and device clock frequencies that are standardized. There is also a decided nomenclature for each of these speeds for each type.

SDR SDRAM DIMMs - These first synchronous registered DRAM DIMMs had the same bus frequency for data, address and control lines.

• PC66 = 66 MHz
• PC100 = 100 MHz
• PC133 = 133 MHz

DDR SDRAM (DDR1) DIMMs - DIMMs based on Double Data Rate (DDR) DRAM have data but not the strobe at double the rate of the clock. This is achieved by clocking on both the rising and falling edge of the data strobes.

• PC1600 = 200 MHz data & strobe / 100 MHz clock for address and control
• PC2100 = 266 MHz data & strobe / 133 MHz clock for address and control
• PC2700 = 333 MHz data & strobe / 166 MHz clock for address and control
• PC3200 = 400 MHz data & strobe / 200 MHz clock for address and control

DDR2 SDRAM DIMMs - DIMMs based on Double Data Rate 2 (DDR2) DRAM also have data and data strobe frequencies at double the rate of the clock. This is achieved by clocking on both the rising and falling edge of the data strobes. The power consumption and voltage of DDR2 is significantly lower than DDR(1) at the same speed.

• PC2-3200 = 400 MHz data & strobe / 200 MHz clock for address and control
• PC2-4200 = 533 MHz data & strobe / 266 MHz clock for address and control
• PC2-5300 = 667 MHz data & strobe / 333 MHz clock for address and control
• PC2-6400 = 800 MHz data & strobe / 400 MHz clock for address and control
• PC2-8500 = 1066 MHz data & strobe / 533 MHz clock for address and control

DDR3 SDRAM DIMMs - DIMMs based on Double Data Rate 3(DDR3) DRAM have data and strobe frequencies at double the rate of the clock. This is achieved by clocking on both the rising and falling edge of the data strobes. The power consumption and voltage of DDR3 is lower than DDR2 of the same speed.

• PC3-6400 = 800 MHz data & strobe / 400 MHz clock for address and control
• PC3-8500 = 1066 MHz data & strobe / 533 MHz clock for address and control
• PC3-10600 = 1333 MHz data & strobe / 667 MHz clock for address and control
• PC3-12800 = 1600 MHz data & strobe / 800 MHz clock for address and control
• PC3-14900 = 1866 MHz data & strobe / 933 MHz clock for address and control
• PC3-17000 = 2133 MHz data & strobe / 1066 MHz clock for address and control

Form factors

Several form factors are commonly used in DIMMs. Single Data Rate (SDR) SDRAM DIMMs commonly came in two main heights: 1.7-inch and 1.5-inch. When 1U rackmount servers started becoming popular, these form factor Registered DIMMs had to plug into angled DIMM sockets to fit in the 1.75' high box. To alleviate this issue, the next standards of DDR DIMMs were created with a 'Low Profile' (LP) height of ~1.2'. These fit into vertical DIMM sockets for a 1U platform. With the advent of blade servers, the LP form factor DIMMs have once again been often angled to fit in these space-constrained boxes. This led to the development of the Very Low Profile (VLP) form factor DIMM with a height of ~.72' (18.3 mm). The DDR3 JEDEC standard for VLP DIMM height is 18.75mm. These will fit vertically in ATCA systems. Other DIMM form factors include the SO-DIMM, the Mini-DIMM and the VLP Mini-DIMM.

See also

• Dual in-line package (DIP)
• Rambus in-line memory module (RIMM)
• Single in-line memory module (SIMM)
• Single in-line package (SIP)
• Zig-zag in-line package (ZIP)

External links

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