HP 8 GB DDR3 1600MHz ECC Unbuffered Dual Rank x8

High-performance memory module designed for powerful systems, servers, and multiprocessor computers with ECC Unbuffered technology support. 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 the error in two bits. Some memory controllers can also repair larger-scale errors in conjunction with ECC memory. Most server boards require memory with ECC support.
The memory has two individually addressable areas (memory rank). Most server chipsets have a limited memory rank, or a specified slot configuration for individual slots, so you need to track this data 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 free memory Slots.
The "x8" chip memory modules are more 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.