What are unregistered and unbuffered RAM

Hi friends,
Recently i was thinking of going for a new memory for my system, when i asked my friends about it they mentioned about Unregistered /and Unbuffered memory. I tried to search on few sites but was not able to understand it.

When i checked out my memory in cpu-z, i saw two different entries describing my ram, registered: no, and buffered: no. that means i amhaving unregistered and unbuffered.

I was checking whether my old ECS motherboard would take high density memory(it won't) and i came across this statement from ECS: "For ECS /PCC motherboards please use NON ECC, unbuffered, unregistered and low density memory modules". why would they say unbuffered and unregistered if there wasn't a difference.

Can anyone help me please....

According to what i know...
Unbuffered RAM: Data can be given to the chips at any time, even in the middle of a clock cycle, there is no control between the chipset and the memory chips. It is less efficient when the data is being read.

Registered RAM: It provides a delay so that all data from the chipset is collected at the beginning/end of a clock cycle. This gives an advantage when data is being read by the system.

Unbuffered and unregistered as synonyms for the average user. Both terms mean that the memory module does not have an extra chip ("buffer") that expands the maximum number of memory modules that can be attached to the memory bus.

In order to install buffered/registered modules you chipset (Intel) or CPU (AMD) needs to be compatible with this kind of module. This kind of module is targeted to the server market. The only exception is socket 940 and socket F CPUs from AMD (used by some Athlon FX models), which require this kind of memory.

Hope this helps you.

Whatever i know with regards to memory there is Unbuffered or registered memory. According to me registered memory is the counterpart of unbuffered memory. There is never "unregistered" memory, and neither will you find "buffered" memory in contemporary computer systems.

Registered memory modules often come with ECC(Error Correction Code) as well, because registered memory is usually applied in servers or high performance workstations where ECC is definitely a necessity.

In a registered memory module the address and command signals is buffered going on to the module. The difference between registered memory and unbuffered memory is whether or no there are registers on the memory module.

The memory controller directly addresses each memory chip on all modules in the system directly in unbuffered memory. In registered memory, the memory controller only sees the register, for which there is one per physical bank of memory.

With increasing system memory, the stability and performance deterioration of memory is inevitable - as mentioned above, the memory controller has to address each memory chip on all modules directly, which results in high electrical loads. To solve this problem, higher density systems use registered memory instead.
Whereas for a home user, registered memory may not be useful at all - in fact, there is a little performance drop with registered memory. But for those who need to utilize more than 4GB of memory in a system, registered memory is absolutely a must-have.

Thanks Amd Athlon for descriptive input, now i have a clear picture regarding Registered and Unbuffered memories.

Thanks for your reply.