What is Parity?
| OddParity, EvenParity, FakeParity |
|
A quality control method that checks the integrity of info stored in a computer's memory. Parity works by adding an extra bit to each byte to make the total number of 1's either odd or even. An error is detected if the circuit determines that this number has changed, indicating that some of the info may have been lost or otherwise corrupted. Two different parity protocols exist, EvenParity and OddParity. Parity protocols are capable of detecting single bit errors only. To enable multiple-bit error detection, manufacturers must use a more advanced form of error checking called Error Correcting Code (ECC). OddParity OddParity and Evenparity are two different protocols used to check the integrity of info stored in memory. A memory manufacturer can use either protocol in a memory product. OddParity adds an additional bit to every byte of data to make the total number of 1s odd. When the byte passes to the CPU, the circuit checks the byte to be sure it is still odd. If it is, the data is considered to be valid and the parity bit is stripped from the byte. If instead it registers as even, it is considered to be invalid and a ParityError is generated. EvenParity and OddParity are two different parity protocols used to check the integrity of data stored in memory. A memory manufacturer can use either protocol in a memory product. EvenParity adds an additional bit to every byte of data to make the total number of 1's in the segment even. When the byte passes to the CPU, the circuit checks the byte to be sure it is still even. If it is, the data is considered to be valid and the parity bit is removed from the byte. If instead it registers as odd, it is considered to be invalid and a ParityError is generated. FakeParity Unlike odd and even parity, FakeParity is not capable of detecting an invalid data bit. It was designed to artificially 'satisfy' a parity-enabled computer without actually checking the data for errors. FakeParity attaches a bit to each byte of data just like odd and EvenParity protocols. The difference is that FakeParity simply adds the correct parity bit as the data is sent to the CPU instead of attaching it before the data is stored to memory, and recalculating it before the byte passes to the CPU. |
Beginner's Help
BUG Club Home
