Before understanding about DIMM, it is good to have information regarding RAMs and its accessories and how it operates.
Just to give you a small bit of background on DIMMs, I will explain what they are. In older computers, it was discovered that two memory modules working in tandem allowed for bigger blocks of data to be simultaneously processed. Oct 07, 2014 What does 2 DIMM mean? I just ordered a computer and it says that it has 8GB RAM (2 DIMM). I know that it means double in line memory module, but does that mean that the computer will come with two 4GB sticks or 1 8GB stick? Thanks in advance! Jul 05, 2017 Remove the DIMM and try again. Laptop designs, due to their lower tolerances for space and volume, are a little trickier. Assuming your laptop allows access to a RAM DIMM slot at all (many newer, smaller designs don’t), the DIMM is generally inserted at an angle, then pushed down towards the laptop frame until it clicks into place. Three SDRAM DIMM slots on a computer motherboard A DIMM or dual in-line memory module, commonly called a RAM stick, comprises a series of dynamic random-access memory integrated circuits. These modules are mounted on a printed circuit board and designed for use in personal computers, workstations and servers.
A RAM is a chip made up of several electronic elements that store the temporary working data of your system which can be read and written. RAM requires electric supply for functioning, hence when the system is turned off, all data from RAM vanishes. It is mounted on the motherboard.
The RAM chips are not individually mounted on the motherboard because of less capacity, hence in earlier times, several chips used to be soldered together and converted into “modules”(integrated circuit boards) and these modules were mounted over motherboard using “pins”(also known as connectors).
Types of modules
There are two types of modules in a RAM:
- Single In-line Memory Module(SIMM)
- Dual In-line Memory Module(DIMM)
In the case of SIMM, the connectors are only present on the single side of the module and are shorted together. SIMMs are always used in matched-pairs. The maximum data storage offered by SIMM is 32-bit/cycle and voltage consumption is 5 volts.
As technology evolved, SIMM became obsolete and was replaced by DIMM. DIMM has the row of connectors on both the sides(front and back) of the module and connectors are independent. This resulted in twice the capacity of DIMM with the same quantity of RAM hence supporting the 64-bit processors. While two SIMM sticks would be used in parallel for 64-bit data width (which is a disadvantage!). The voltage consumption of DIMM is 3.3 volts which are comparatively lower. It is not backward compatible i.e it cannot be used on motherboards having SIMM slots. It is easier to replace damaged or corrupted RAM piece on DIMM.
This proves that DIMM cleary outperforms SIMM in speed, latency, and power consumption. DIMM is generally available in 168, 184, 214 or 244 pins.
Classification of DIMM
DIMM can be classified on the basis of buffer size and type of RAM:
- DIMM classification based on buffer size:
- Unbuffered DIMM (UDIMM): The system directly reads/writes from/to memory chip without validation hence increasing the electrical load on the motherboard but are very faster.
- Registered DIMM (RDIMM): uses register that buffers signals, hence increasing clock cycle but are more reliable.
- DIMM classification based on the type of RAM:
- SDRAM (synchronous dynamic RAM) DIMM: It was the first dynamic RAM to sync with the system clock. The refresh rate was much lower due to re-accessing data after the rising half cycle.
- SDR(single data rate) DIMM: single data rate means the packet of data is only accessed once per clock cycle. Serial data can be read via the serial data pins on the DIMM which enables the motherboard to autoconfigure to the exact type of DIMM installed.
- DDR(double data rate) DIMM: Data packet is accessed twice each clock cycle. DDR DIMMs also use two notches on each side to enable compatibility with both low- and high-profile latched sockets.
- DDR2 DIMM: The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so data can be transferred four times faster per memory cell cycle.
DDR3 and DDR4 are the improvised versions of DDR with less latency and better accuracy. SODIMM (small outline DIMM) is much more compressed with noticeable size-reduction to use it in portable devices.
How to select proper DIMM?
DIMM sizes vary from micro ATX to standard motherboards so no. of pins is an important factor. While purchasing a RAM stick, ratings are like 16 GB RAM can be 1X16GB(1 DIMM and 16 GB RAM each), 2X8GB(2 DIMM and 8 GB RAM each) or 4X4GB(4 DIMM and 4 GB RAM each). Operating frequency and maximum overclocking frequency should also be taken into consideration.
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-written by Jeff Goldenbaum, Dataram Memory Blog Team Member
Comparing Quad-Rank and Dual-Rank Memory Modules
The term “rank” simply refers to a 64-bit chunk of data. In its simplest form, a DIMM with DRAM chips on just one side would contain a single 64-bit chunk of data and would be called a single- rank (1R) module. DIMMs with chips on both sides often contain at least two 64-bit chunks of data and are referred to as dual-rank (2R) modules. Some DIMMs can have DRAM chips on both sides but are configured so that they contain two 64-bit data chunks on each side—four in total—and are referred to as quad-rank (4R) modules. Quad-rank DIMMs run at a maximum PC3-8500 (DDR3-1066) speed in current architecture.
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Why Have Quad-Rank DIMMs?
With each new generation of DRAM chip, quad-rank DIMMs are the least expensive way to achieve the highest density DIMM. Today, a 16GB dual-rank DDR3 DIMM is built with thirty-six 4Gb (gigabit) chips. A quad-rank 32GB DIMM will utilize thirty-six “dual-die” (essentially two DRAMs within each physical chip) 4Gb chips. Until the next generation 8Gb chips become more mainstream and production costs come down, we won’t see a cost-effective dual-rank 32GB DIMM. But when that does occur, you’ll not only see dual-rank 32GB DIMMs, but you’ll also see quad-rank 64GB DIMMs!
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Quad-rank DIMMs actually perform best in Xeon 7500 CPU based systems as the memory BOB (buffer-on board) architecture delivers better performance compared to single- or dual-rank DIMMs of equal capacity. The maximum speed is still PC3-8500 and is consistent regardless of whether the system has the minimum configuration or is fully loaded.
When to Consider Ranks
Today’s 2-way servers with Intel Xeon 5600 series processors that utilize DDR3 memory technologies have limitations when it comes to how many ranks of memory may be installed. DIMM slots are configured as “channels” with either 3 channels of 2 DIMM slots each (server models with 12 DIMM slots), or 3 channels of 3 DIMM slots each (server models with 16 or 18 DIMM slots). Each channel supports no more than 8 ranks of memory. Simply put, no more than 12 quad-rank DIMMs can be installed in these servers. To utilize all available slots in servers with 16 or 18 DIMM slots, the use of dual-rank DIMMs is required.