Learning conclusions about memory types UDIMM, RDIMM, LRDIMM With the continuous development of memory technology, the capacity, density and speed of memory on the server are also getting higher and higher.
The highest density of memory sticks currently on the market can achieve 4 Ranks per memory stick, with a capacity of 32GB per stick and a maximum speed of 1.6GHz. High density and high frequency also means higher prices and possibly higher power consumption.
So how should you choose a memory module according to actual needs? Types of memory At present, the memory bus technology of servers has basically not changed much, and DDR3 technology is still used. DDR3 is a parallel transmission technology, so to ensure the effectiveness of parallel data transmission, it is necessary to work hard on memory modules.
At present, there are three types of memory modules: UDIMM, RDIMM, LRDIMM.
1 UDIMM
Also known as Unbuffered DIMMs.
When data is transmitted from the CPU to each memory granule, UDIMM requires that the data transmission distance between the CPU and each memory granule be equal, so that parallel transmission will be effective. This requires extremely high manufacturing processes, and it is extremely difficult to achieve high density and high frequency. So UDIMM capacity and frequency are lower. However, UDIMM has less latency at the same frequency because there is no cache between the CPU and the memory. At present, the common capacity is 2GB/4GB, and the highest frequency can only reach 1.33GHz.
2 RDIMM：
Also known as Registered DIMMs.
In order to ensure the effectiveness of parallel transmission, RDIMM adds a register to the memory module for forwarding. It is located between the CPU and memory granules, thus reducing the distance of parallel transfers. At the same time, due to the high register efficiency, the density and frequency of RDIMMs can be easily increased. RDIMM is currently the more mainstream memory module, with a single capacity between 2 and 32GB, and a frequency of 1.33GHz and 1.6GHz. Most 2-way general purpose servers are usually shipped with this type of memory.
3 LRDIMM：
Also known as Load Reduced DIMMs.
Although RDIMM improves the transmission effectiveness, due to the limited register size, when the memory particles in a single memory are deployed with the highest density 4 Rank, the effectiveness and frequency of parallel transmission will be greatly reduced. For example, when using 32G RDIMMs, only 2 memory sticks can be deployed on each memory channel of the server, and they can only run at 800MHz.
in conclusion:
1
From a price point of view
RDIMMs are more modest.
Small-capacity UDIMMs are cheaper, but due to high manufacturing process requirements, large-capacity UDIMMs are even more expensive than RDIMMs. The price of LRDIMM is higher than that of RDIMM and UDIMM.
2
From a capacity point of view
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 a frequency point of view
At present, only RDIMM supports 1.6GHz, which can have larger bandwidth and small delay.
4
From a frequency point of view
Although UDIMM has the smallest delay at the same frequency, RDIMM can support 1.6GHz and use a higher frequency to reduce the delay.
5
From a power consumption perspective
LRDIMMs are the highest, RDIMMs and UDIMMs are lower.
Conclusion :
If the maximum memory capacity is required, LRDIMM must be used; if the maximum memory capacity is not required, RDIMM (1.6GHz) has better performance, price and scalability; if power consumption is considered, low-voltage DDR3L memory can be used, and control It operates at a lower frequency.
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