Differences between SO-DIMM, U-DIMM, R-DIMM, and LR-DIMM memory modules

SODIMM (Small Outline Dual In-line Memory Module) Small outline dual in-line memory module

It is a type of computer memory module, mainly used in notebook computers and other applications that have higher requirements for size. Is a type of computer memory module. Compared to DIMMs, SO-DIMMs have a smaller form factor (roughly half the size of normal DIMMs). Therefore, SO-DIMM is mainly used in laptop computers and other applications that have high requirements for size. So-dimms are available with 72 pins (supporting 32-bit data transfer) or 144 pins or 200 pins (supporting 64-bit data transfer).

In order to meet the memory size requirements of notebook computers, SO-DIMM (Small Outline DIMM Module) has also been developed, which is much smaller than the standard DIMM size, and the number of pins is not the same. So-dimms also vary according to SDRAM and DDR memory specifications, with SDRAM SO-DIMMs having only 144pin pins, while DDR SO-DIMMs have 200pin pins. In addition, the notebook memory has two interfaces, MicroDIMM and Mini Registered DIMM. The DDR of a MicroDIMM port is 172pin, and the DDR2 port is 214pin. The Mini Registered DIMM has a 244-PIN port and is mainly used for DDR2.
Unbuffered DIMM

Refers to the desktop market without buffering, is the most common memory module on the market.

Early SDR memory mods, with Buffered types, have become rare. The Buffered memory module and the Registered memory module mentioned later are not the same thing, the Buffered memory module is the address and control signals through the buffer, without any timing adjustment (buffer latency is some); The Registered memory module stores addresses and control signals and triggers the output when the next clock arrives.
Registered DIMM

Its address and control signal through the register, the clock through the PLL phase lock, positioned in the workstation and server market.

Registered memory modules, compared with Unbuffered memory modules, the advantages are that it is easier to achieve higher capacity and stability at both the module level and the motherboard level, but for a single read and write access, it will lag one clock cycle.

LRDIMM (Load - Reduced DIMM)

Instead of using more complex registers, LRDIMMs use simple buffers. Buffering reduces the electrical load on the underlying motherboard, but has little impact on energy and memory performance. Unlike RDIMMs and LRDIMMs, which allow server manufacturers to put more modules on each memory channel. As a result, LRDIMMs are designed to contain large volume system memory without incurring high latency costs.

By using new technology and lower operating voltage, LRDIMM can reduce the load and power consumption of the server memory bus, and enable the server memory bus to achieve higher operating frequency and greatly increase the memory support capacity.

Comparison:
1. From the point of view of price, RDIMM is relatively moderate. Small capacity UDIMMs are cheaper, but due to the high manufacturing process requirements, large capacity UDIMMs are even more expensive than RDIMMs. Lrdimms are more expensive than RDIMMs and UDIMMs.

2. From a capacity perspective, only LRDIMMs can support the maximum total memory capacity. However, the memory capacity required for major applications can generally be achieved by deploying RDIMMs.

3. From the perspective of main frequency, only RDIMM supports 1.6GHz at present, which can have greater bandwidth and hour delay.

4. From the perspective of delay, although the UDIMM has the smallest delay at the same frequency, RDIMMs can support 1.6GHz, and use a higher frequency to reduce delay.

5. From the perspective of power consumption, LRDIMMs are the highest, while RDIMMs and UDIMMs are the lowest.