Parity (was Re: stepping machanism of Apple Disk ][ drive)

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Fri Apr 9 08:22:09 1999

> Bottom line: Apple not using parity is not a reason to trash the Mac. How
> many PCs have parity since we moved to EDO and SDRAM? It's extra cost and
> extra complexity and extra possibilities for failure. Unless you can correct
> the failure, it's not mathematically worth the extra expense and reduced
> reliability.

there is one reason to use parity... Data integrity. While a missed bit
can cause the machine to go down you are not burdened with BAD data. If
the bad bit happens in the data area rahter than code and it happens to be
the high order bit of a floating point number it's quite imaginable that
100 dollar credit could easily become a debit of some larger amount.

ECC however is fault tolerence but the price paid in the past was high
in both memory system speed and COST. Which cpus going ever so fast that
cost is still high but, having wyour SQL data base corrupt do to bad
memory could really hurt!

Allison
Received on Fri Apr 09 1999 - 08:22:09 BST