Lenovo 4GB DDR3 1600MHz ECC Unbuffered Dual Rank x8

Powerful and reliable DDR3 server-based memory module for powerful systems, servers and multiprocessor computers. This memory is primarily designed for Lenovo E31, S30, C30 or D30 performance workstations. It is tested for the most demanding use, making it ideal for important applications.
ECC technology checks transparently and in real time the integrity of data stored in memory. It can find and fix an error in one bit and detect a two-bit error. Some memory controllers can also repair larger-scale errors in conjunction with the ECC. Most server boards require memory with ECC support.
The memory has two separately addressable memory ranges with a bus width of 72 bits (64 bit data and 8 bits ECC code). Most server chipsets have a limited memory rank or a specified memory configuration for individual slots, so you need to track this figure for future upgrades - if you have full memory rank on the motherboard, you will not be able to add another module even if there are some free Memory slots.
The "x8" chip storage modules are affordable, but they do not support advanced server technologies such as multiple-bit error correction, Chipkill, memory scrubbing, or Intel Single Device DataCorrection (SDDC), making it ideal for entry-level servers.
Additional information:

Intended for:
Lenovo ThinkStation E31, S30, C30, D30

Note: In one PC you can not mix ECC and non-ECC memory and RDIMM with UDIMM!!!