40k Ferrite Memory Core

[Brent Hilpert]

Pete Turnbull wrote:
> 
> On 29/10/2008 19:52, Rick Bensene wrote:
> 
> > I agree with Brent's analysis.  I too counted 21 planes, which seems a
> > bit odd, as typically each plane represented one bit in a word
> > structure, which would indicate a 21-bit word...not something that
> > matches up with commonly-used word sizes in 50's/60's era computers (12,
> > 16, 18, 20, 24, 32, 36, 48, 60 or 64 bits).
> 
> It looks pretty intact, and I don't think anything's been stripped.
> However, while I count 21 layers (image 2 and image 4) in the
> construction, the top layer has no cores (plain to see in images 3 and
> 4), so there are 20 planes by my reckoning.
> 
> And counting rows and columns of cores (not just the wires), I see 40 x
> 50 (you can easily count them in image 4), which matches the X and Y
> numbering on the connectors.  So I still reckon that stack is 2000 words
> x 20 bits.

Agreed, looks like the upper 21st 'plane' is just a header for the address wires.
I had arrived at y=48 from looking at the blurry numbers on the Y
connector on photo 5, but a recount indicates 50.

That left me wondering where the 4 connections for the sense and inhibit
wires are: looking again at the other photos, it appears there are two extra
pins on *each* axis (42 & 52) of each plane, so 4 extra pins per plane.

(In photo 4, looking down the planes starting at the left end of the row of
yellow wires one can see the cut-off wires soldered to the pins of what should
be either the sense or inhibit lines.)