Memory Upgrades for PC or MAC from Data Memory Systems: "HOW DO I KNOW IF I NEED PARITY, NON-PARITY, OR ECC, NON-ECC MEMORY?

The general rule of thumb in deciding what type of memory you need is to look at what’s already installed in your system. To find out if you have ECC, parity, or non-ECC, non-parity memory, count the number of chips on the module. Divide the total number of chips by three. If you can evenly divide the number of chips by three, the module is ECC or parity, if not, then it is a non-ECC, non-parity module. If you're building a PC and plan to use your system as a server or a similar mission critical type machine, it is to your advantage to use ECC. If you plan to use your PC for regular home, office, or gaming application, you are better off with non-ECC, non-parity memory.

HOW TO TELL ECC, PARITY MEMORY FROM NON-ECC, NON- PARITY MEMORY?

If your system has ECC or parity memory the chips are evenly divisible by three. How do you know which one you have? One way is to look at the part numbers on the chips of your module. If each chip has the same part number, you have ECC. If one chip is different, you have parity.

WHAT IS THE PERFORMANCE DIFFERENCE BETWEEN ECC, PARITY AND NON-ECC, NON-PARITY?

ECC (error checking and correcting) memory performs double bit detection and single bit correction. This means that if you have a single bit memory error, the chipset and memory will find and repair the error on the fly without you knowing that it happened. If you have a double bit memory error, it will detect and report it. Non-ECC, non-parity memory, on the other hand, has no error detection and correction capabilities.
Using ECC decreases your PC’s performance by about 2%. Current technology DRAM is very stable and memory errors are rare, so unless you have a need for ECC, you are better served with non-ECC, non-parity memory."