ما سه نوع رم معمول داریم :
1- Non ECC که برای دسکتاپ ها بیشتر استفاده میشه
2- ECC Registered
3- ECC Un-Registered
که این دو نوع با توجه به ساختار CPU در سرورها استفاده میشن (برای بعضی CPU ها فقط ECC-UnReg میشه استفاده کرد و برای بعضی هم میشه هر دو نوع رو استفاده کرد).

نوع اول مصرف کمتری داره و میتونه در حجمهای خیلی بالا و تعداد بالا (مثلا 16 استیک با حجم 16 گیگابایت که جمعا میشه 256 گیگابایت) روی سرور استفاده بشه.
در حالی که نوع دوم این قابلیت رو نداره

حافظه Registered  اغلب گران تر است به دلیل حجم پایین و اجزای اضافی

Unbuffered memory

Unbuffered memory (or unregistered memory) is RAM where there is no hardware register between the memory controller and the RAM chips. Unbuffered memory is the opposite of registered memory. Registered memory is more stable, one clock cycle slower, and more expensive than unbuffered memory. Registered memory is usually used in servers and workstations, while normal PCs usually use unbuffered memory.

Some high-end hardware, such as servers, require the use of registered memory.

In the past, registered memory was called buffered memory and unregistered memory was called unbuffered memory. Registered memory got renamed in common use, but unbuffered memory did not.

Buffered (Registered) Memory has ECC (Error Correction Code aka "error checking and correcting") and is often but not always one clock cycle slower than unregistered memory. Unregistered memory comes in ECC and non-ECC varieties. While ECC can cause a minor reduction in performance, it can prevent costly errors when running memory intensive software. For this reason it is often used in servers and workstations where up-time and reliability outweigh the desire for a slight performance increases. On desktops, gaming, and enthusiasts computers non-ECC is often preferred because a minor speed increase is desired over a slight increase in stability

Ram buffered

    Not to be confused with ECC memory, although memory modules often use both technologies.

Registered (also called buffered) memory modules have a register between the DRAM modules and the system's memory controller. They place less electrical load on the memory controller and allow single systems to remain stable with more memory modules than they would have otherwise. Registered memory is often more expensive because of the lower volume and the additional components, so it is usually found only in applications where the need for scalability and stability outweighs the need for a low price (servers, for example). Although most memory modules are both ECC and registered, there are also both registered non-ECC modules and non-registered ECC modules. Non-registered ECC memory is supported and used in motherboards which do not support the very large amounts of memory used by servers.

Nominally, there is a performance penalty for using registered memory. Each read or write is buffered for one cycle between the memory bus and the DRAM, so the registered RAM can be thought of as running one clock cycle behind the equivalent unregistered DRAM. With SDRAM, this only applies to the first cycle of a burst.

However, this performance penalty is not universal. There are other factors involved in memory access speed. For example, the Intel "Westmere" 5600 series of processors access memory using interleaving, wherein memory access is distributed across 3 channels. If 2 memory DIMMs are used per channel, this "...results in a reduction of maximum memory bandwidth for 2DPC (DIMMs per channel) configurations with UDIMM by some 5% in comparison to RDIMM." [1] (p. 14). This is because "...when you go to 2 DIMMs per memory channel, due to the high electrical loading on the address and control lines, the memory controller uses something called a “2T” or “2N” timing for UDIMMs. Consequently every command that normally takes a single clock cycle is stretched to two clock cycles to allow for settling time. Therefore, for two or more DIMMs per channel, RDIMMs will have lower latency and better bandwidth than UDIMMs.".