Memory types - PC3L-12800R vs PC3L-12800E

Question

I'm trying to determine if a specific memory module (which I have not yet acquired) will work with my server.

My server is an Acer Altos T310 P3 server, and currently has a single 8GIG DIMM in it. The DIM inside is an 8GB 2Rx8 PC3L-12800E-11-13-E3 module made by Kingston. The memory module I'm looking to acquire is a 1Rx4 PC3L-12800R-11-13-C2 8 gig module made by Hynix.

What does the "E" and the "R" stand for, and what are the chances that the memory is compatible with current memory and server (I'm speculating the E is ECC, the R is registered, but I don't understand what the difference is - if there is any). Both the existing and new memory claims to be ECC memory.

(Acers specs for the system are here - I see that they recommend against mixing 1R and 2R memory - I'm wondering if I should take the punt - the module is only about US$40)

Solution

As @davidschwartz pointed out in the comments, the "R" memory is registered which "means it has additional buffers". Sometimes registered memory is called buffered memory.

To extrapolate, the "E" memory does not have the additional registers and is unbuffered. They both are ECC, but they both are NOT registered. You usually cannot mix them, but sometimes enterprise server boards can accept both; with "R" usually allowing more installable memory capacity I think.

Further there was/is? a "U" which is unbuffered non-ECC.

My work station circa 2011 takes ECC "E" (unbuffered at the time) and my server circa 2006 takes ECC "F" or fully buffered, which then for a time was labeled "R". It just depends on the times.

I have read that registered memory was a crutch to quicken the pace of technology (more capacity/channels) at the time for the cost of performance and power consumption. I'm not sure its used as much now but now there appears to be a "P" ?!?!

For further information you might look up registered memory, buffered memory, FB-DIMM, or fully buffered memory (they are all the same to my knowledge)