Quote:
Originally Posted by Dennis
Wow, so the owner of the AGC worked on the LEM and purchased 2 tons of discarded NASA Apollo HW at a warehouse somewhere, found the AGC and the young guy testing the Apollo AGC core memory has also built an AGC Emulator. 
Astonishing to see their demo of how ferrite core memory works, the wiring and stacking in those modules blows my mind. Then the Formal Peer Design Review considers them not suitable for flight…Where was Silicon memory when you needed it. 
And, reading it is destructive. Wow.
How on earth DID they get to the Moon…and back.
Cheers
Dennis |
Hi Dennis,
It's pretty cool.
I have attached a couple of snapshots I just took of a core memory board
I own which came out of an IBM 360/50 mainframe from the 1960's.
When it was new, it would have cost some eye-watering amount of money.
This has higher density than the core memory that was in the AGC
and the cores themselves are even too small to see naked eye.
Where you mentioned reading was destructive, that is right.
Three wires pass through each core. One to flip it to the '1' state,
another to flip it to the '0' state and a sense wire.
So to read a bit back, you would attempt to flip it to the '1' state whilst
monitoring the sense wire. If it was already in the '1' state then the
magnetic flux would barely change and the sense wire would detect
nothing. If it was in the '0' state and you just flipped it to '1', you would
detect the change in flux in the sense wire and then you would have to
restore it by flipping it back to '0' again.
It did have one enormous advantage over the DRAM sitting in your
PC right now in that if you cut the power it would retain its contents.
Remarkably the AGC firmware was woven into the core as a form of
read-only memory (ROM).