Whats the differece between 128MB of RAM with 16meg x 64 and 16meg x 72

[Ozzman1113]

Does it have to do with ECC?

 

[divide by zero]

Yes, the 16x72 is ECC memory. The 16x72 has 9 or 18 mem chips. The 16x64 has 8 or 16 mem chips. The extra memory chips are for the parity bit - you use eight bits plus a parity bit for each byte in ECC memory.

 

[Peter]

No you don't, you use an 8-bit ECC value for each 64-bit data word.

While this requires just as many extra memory bits as does classic 8+1 parity, the math is different. It allows detecting more errors, and even auto-correcting some.

8+1 can detects single-bit errors, misses many multiple-bit errors, and allows no corrections.

64+8 allows detecting and correcting all single- and some multi-bit errors, and detects any multi-bit errors.

Regards, Peter