[SML] turning off light boards

[Alf Sauve']

True they did flip states whenever the bits were read, but the memory 
board circuitry was responsible for flipping the state back to it's 
original setting.   The memory wasn't volatile, as you said, in the 
sense that it could retain its state for a long time without power.  Not 
much of a feat today, but in the 50's, 60's and 70's it was amazing.   
DOD required 100s of state changes to every bit before a system with 
classified data could be considered scrubbed.

Staggering to think that the original Space Shuttle simulator utilized 
about a half dozen super computers (for their day). each with a whopping 
2MBs of core memory.

On 11/24/2015 6:30 PM, Lou Poppler via Stagecraft wrote:
  ISTR that the old ferrite cores would be demagnetized by a read 
operation, and always had to be "refreshed" after a read, IE every time 
you read, you have to write the info back to that memory, unless you are 
exchanging it with new, different data in the write-back. It is true 
that they would remember their state for a long time if you left them 
alone, even with the computer powered off.