Unbuffered memory is commonly used for laptops and PCs where buffering data is not so critical. These modules are basically faster than buffered memory since data pass from RAM to chipset or motherboard directly and without much intervention.

Buffered memory and registered memory are essentially the same in that they contain logical components called “buffers” or “registers” that help the chipset manage the proper address loading of data. This is particularly helpful when large volume of data is being processed that is why modules of this type are usually required on most servers where reliability is very critical. These modules have higher latency, which makes the initial response to be slower than unbuffered modules.

The term “ Buffered” often refers to asynchronous modules, that is, EDO and FPM memory, while “Registered” is used for  synchronous memory or SDRAM.

Physically, you can easily identify a module is registered because it has additional chips usually located at the bottom of the module which increases its height. Some rackmount solutions require the standard height modules so these extra chips are placed between the row of DRAM chips. These modules are known as low profile registered DIMMs.

Registered and Unbuffered modules cannot be used simultaneously in one system.