Core Memory Interfacing?

From: Allison <ajp166_at_bellatlantic.net>
Date: Wed Apr 3 15:56:57 2002

From: Joe <rigdonj_at_cfl.rr.com>
drivers and sense amps on it so that might make things easier. However there
are some things that you have to do with core and I don't know if they
handled in hardware or if the OS had to take care of it. For example,
reading core is destructive, that is it erases the contents so you have to
store the contents back into it before you do anything else (unless you
don't care if it's lost). That seems like it wou!
> ld be easy enough to do in HW but I don't know if that's what they did.

Not an OS task. It's usually handled in hardware either in the CPU
microcode or as a synchronous
timing with the cpu such that if the cpu is going to alter the data at the
location it's already started
the cycle. Some will stop the memory cycle after the read to see if it
should write the old data
back or alter it, this is usually signaled by the cpu before it outputs a
new address.

That would be ideal as you have something you may have data on, most of the
circuits and
even a clue on the timing. I'd love to play with something like that rather
than a scratch build.

Allison


>
> Joe
>
>At 11:41 AM 4/3/02 -0600, you wrote:
>>Right off, let me say that I know next to nothing about the realities of
>>using core memory. I only know that it looks like pretty cool stuff to
>>play with. Would I be completely off my tree to try to build a core
>>memory interface from scratch, assuming I had a pre-strung core frame with
>>all the cores and wires intact? When I say "interface", I mean basically
>>something that will let me talk to the core from a PC or from my
>>recently-completed Mark-8 using TTL or CMOS levels. If I have a 64x64
>>frame, would I just need something on the order of 256 driver transistors
>>(one to drive each of the X and Y wires in either direction) plus some
>>kind of op-amp or comparator circuit to monitor the sense wire (is there
>>just one of these per frame?) and determine whether or not a bit has
>>flipped during a read pulse? Or are there all sorts of ghosts and goblins
>>lurking in core memory that I don't want to confront?
>>
>>
>>
>>
>
Received on Wed Apr 03 2002 - 15:56:57 BST