Here's why Macintosh systems don't implement parity checking:
- Reliability. RAM is typically the most reliable component in our systems.
- Simplicity. Parity checking requires additional hardware overhead, which
lowers reliability.
- Low chip count. The systems for which parity checking was originally
designed required more chips for the same amount of RAM. RAM chips used in
these older system were far less reliable than the chips used today.
- The Macintosh does a full read/write RAM test every time it is switched on.
This test is a sufficient diagnostic.