memory question

In article <b2bo90hvl491sm222icg1aeuutbgreq8gt.TakeThisOut@4ax.com>, Sam Owens
<sam.TakeThisOut@sam.com> wrote:

 > What's the difference between 32meg x 64 and 32meg x 72? Thanks
 >
 > Sam

The x64 is non-ECC, while the x72 is ECC. ECC is used on server
boards, to catch errors in data read back from the memory. For
desktop boards, the error rate is considered low enough that many
designs don't support ECC. Check your motherboard manual to see
whether ECC is supported or required for proper operation.

ECC has the ability to check and correct memory errors. The extra
8 bits available, store a syndrome or signature, and when the
72 bits are read back later, a calculation is done, to see if the
syndrome is consistent with the data word. For some small number
of errors, the Northbridge can actually figure out which bits
are in error, and correct them. If more bits are in error, then
the error can be "uncorrectable", and if the processor is about
to "eat" that data, generally the processor would be told to
crash or error out of the affected application.

With the ability to correct errors in memory, it is possible
for the hardware to "scrub" the memory. This is a background
process, where data unrelated to what the processor is currently
doing, is read, corrected if necessary, and written back to
the memory. This feature helps a server board that has a lot
of memory, from "accumulating" errors in data stored for long
periods of time. As long as the number of errors in a data word
in memory can be kept small, the "scrubber" can keep removing
them.

HTH,
Paul<!-- ~MESSAGE_AFTER~ -->