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Motherboards are manufactured to use a specific type of memory. You must match your memory to your motherboard. In addition to selecting the correct memory generation (DDR3, DDR4, etc.), other factors must be considered.
High-density memory tends to be less expensive than other memory but is non-standard. It only works with specific motherboards.
Parity memory uses an extra bit in each byte as an integrity check against the other eight bits. If there is an odd number of ones in the eight data bits, the parity bit will be one with even parity and zero with odd parity. On older systems that used parity, the system would halt upon detecting a parity error. Parity will detect an odd number of bad bits but cannot identify which bits are bad. Parity will fail to detect multiple bad bits if there is an even number of bad bits. Parity memory is obsolete.
Error Correction Code (ECC) uses a ninth bit per byte but also divides the memory into blocks of nine bytes. The ninth byte acts as a parity check for the other eight. Using ECC, a bad bit can be identified by column and row and corrected. ECC will fail to identify specific patterns of bad bits. Other patterns can be detected but not corrected. However, multiple bad bits in a single block are rare, and undetectable or uncorrectable patterns are even rarer.
Modern computer RAM is exceptionally reliable, so ECC memory is usually reserved for systems that require extraordinary reliability. If you mix ECC and non-ECC memory on the same ECC-capable motherboard, ECC may be disabled for the entire memory.
Buffered memory (aka registered memory) has a register or buffer between the memory and the controller. This reduces the memory controller's electrical load, allowing more memory in the system. In addition, buffered memory usually uses ECC memory. Buffered memory is typically used in high-end workstations and servers.
Unbuffered memory is faster than buffered memory and is used in most computers. Unbuffered memory may or may not use ECC.
On older motherboards that use SIMM modules, the memory is laid into the socket at an angle and then rotated vertically into place to be held by the retaining clips.
Install DIMM modules by aligning the key slot and pushing straight down until the retaining clips snap into place.
Install dual channel memory as matched pairs in the proper slots. The slots are usually color-coded, but some motherboards group the colors differently from others. Check the motherboard manual for the coding.
Don't mix parity and non-parity (ECC and non-ECC) memory in the same bank.
Don't mix memory speeds in the same bank.
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