Memory type: Udimm, Rdimm, lrdimm_pc base

At present, the server's memory bus technology is basically not much change, still use DDR3 technology. DDR3 is a parallel transmission technology, so in order to ensure the validity of parallel data transmission, we must work the memory bar. At present, there are three kinds of memory: Udimm, Rdimm, Lrdimm.

1.UDIMM: Also known as unbuffered DIMMs. When data is transferred from CPU to each memory particle, UDIMM requires that the data transfer distance between the CPU and each memory particle be equal, so that the parallel transmission will be effective. This requires a very high manufacturing process, it is extremely difficult to achieve high-density, high frequency. So the UDIMM capacity and frequency are lower. However, due to the lack of any caching between the CPU and memory, UDIMM has a smaller delay at the same frequency. Currently common is a single capacity 2GB/4GB, the highest frequency can only reach 1.33GHz.

2.RDIMM: Also known as registered DIMMs. In order to ensure the validity of parallel transmission, RDIMM a register on the memory strip for forwarding. It is located between the CPU and the memory particles, thus reducing the distance of the parallel transmission. At the same time, because of high register efficiency, the density and frequency of RDIMM can be improved easily. Rdimm is currently the more mainstream of the memory, a single capacity between 2~32GB, frequency also has 1.33GHz and 1.6GHz two of choices. Most of the 2-way general-purpose servers typically configure this type of memory when they are shipped.

3.LRDIMM: Also known as the load reduced DIMM. Although RDIMM improves transmission efficiency, due to the limited register size, when the memory particles in a single memory are deployed at the highest density of 4 rank, the effectiveness and frequency of parallel transmission will be greatly reduced. For example, when using 32G Rdimm, you can deploy up to 2 memory strips per memory channel on the server and only run at 800MHz. Lrdimm memory reduces the load on the memory bus by changing the register chip on the current RDIMM memory to a IMB (isolation Memory buffer) memory isolation buffer, and further increases the memory support capacity accordingly. Compared to the usual Rdimm,dual-rank Lrdimm memory power consumption only its 50%,quad-rank Lrdimm can also be low to 75%. Currently, a typical NEHALEM-EP processor can support 3 memory channels, with a maximum of 3 Rdimm per memory channel, and with Lrdimm memory, the same system can support up to 9 DIMMs per channel and memory capacity up to three times times the original.

What is Lr-dimm, Lrdimm Memory? (Load-reduce DIMM)

http://www.simmtester.com/page/news/showpubnews.asp?num=167