ECC stands for "error correcting code." Like parity memory, ECC memory detects and reports memory errors. However, while parity can only detect errors, ECC can actually correct errors without interrupting the other operations of your system.

If you do not see an option for ECC memory when searching for your memory upgrade, your system most likely has non-ECC memory installed and will not support ECC memory. In this case, you should upgrade your system with non-ECC memory (standard).

If your system has ECC memory, you should choose the upgrade option with "w/ECC". If you determine that your system is using non-ECC (standard) memory, you should select the upgrade without ECC in the description.

There is a slight decrease in performance, but it's usually approximately 3-4% on PC133 CAS2 ECC SDRAM insignificant since 3% is barely within the margin of error on benchmarks

ECC more expensive than Non-ECC, but not all motherboards support ECC ram. check with your Motherboard manufacturer before purchasing Ecc Memory. It's often used in high end systems, or servers.