Can We Effectively Correct Errors in Computer Memory?

  • Thread starter Thread starter Loren Booda
  • Start date Start date
  • Tags Tags
    Computer Memory
Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
Sign up Log in
3 replies · 2K views
Loren Booda
Messages
3,115
Reaction score
4
Computer memory has steadily grown larger, although more important may be guarding against environmental errors for its posterity.

If we save three copies of memory rather than just one, to what degree (in % of memory bits) could subsequent errors (at most one out of three per position among memories) be corrected effectively?

Also, does my PC have such a backup?
 
Engineering news on Phys.org
No your PC does not have such a backup. There is a trick that is a little more elegant, where there are so called parity bits. For every byte of 8 bits there is a ninth bit that contains the logical xor of all the bits. If a bit gets damaged then this is detected immediately and the memory location can be marked as bad. This has been removed a long time ago for cost reasons. So three times the memory is out of the question.

Your scheme will correct bit flips unless two occur in the same triplet. So you define some failure rate that you are willing to accept and calculate what probability of a single bit flip you can allow for, such that the chance of two in one triplet are that high.

There are much more elegant error correction schemes. Look for "cyclic redundancy check", and "Cross-interleaved Reed-Solomon coding" (this is done on CDs)
 
Anything important is typically stored on your hard drive, so no such backup is needed. Afterall, what use is a volatile backup when a power failure can wipe it out?