error correcting memory
<storage> (ECM) RAM using some kind of error detection and correction
(EDAC) scheme. The two types of memory errors in RAM (especially DRAM) are
"soft" errors due to radiation-induced bit switching, and "hard" errors due to
the unexpected deterioration of a memory chip. Soft errors do not indicate
lasting damage to the memory board, but they do corrupt programs or data. Hard
errors demand physical repairs. Single bit memory failures are the most common.
A hard single bit failure, such as that caused by a completely dead chip can be
corrected by EDAC if each chip supplies only one bit of each word. EDAC memory
is the most common level of protection for minicomputers and mainframes whereas
the cheaper parity protection is more common in microcomputers.
[Clearpoint, "The Designer's Guide to Add-In Memory", Third Addition].
(1995-10-10)
Nearby terms:
ERP « error « error-based testing « error
correcting memory » error detection and
correction » es » ES-1
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