On Fri, 25 May 2001 19:12:36 +0100 (BST) Tony Duell
<ard_at_p850ug1.demon.co.uk> wrote:
> [Williams tube memory]
>
> > The memory was also the only output device in the "Baby",
> > since the CRTs had normal phosphor coating and the bits
> > glowed. Programs would halt, and the results would be read
> > from the CRT face.
>
> Are you sure? I thought there was a metal electrode over the front of the
> CRT, and the signal picked up from that was fed back to refresh the
> charge image on the CRT face (yes, this is a simplification).
That's how I understand it, yes.
> So if you moved the electrode to see the screen, you'd lose the memory
> contents.
Absolutely. There's a photo of a dual Williams tube module
in one of the books, hinged open in just this way.
> I can well believe having a second CRT coupled up, which had the same
> deflection signals, and in which the beam intensity was controlled by the
> amplified singal from the pickup electrode. That would display the memory
> contents as an array of dots.
I think that must be how it worked. However, I've never
seen this clearly and completely explained! There's a CRT
lying in one of the racks in the middle of the photos of
the "Baby", above the input switch bank. The actual store
is in another rack, though.
> And VCR97s [1] were not exactly uncommon,
> adding a second one would not have been a problem
It would have been quite easy to wire up, yes.
> [1] Valve Cathode Ray 97 IIRC. A very common radar CRT from WW2. Common
> enough that _I_ have one in the junk box.
Since you have one, could you tell me if it's
electrostatically deflected? I presume it is, making it
resemble an oscilloscope tube more than, say, a TV picture
tube?
--
John Honniball
Email: John.Honniball_at_uwe.ac.uk
University of the West of England
Received on Tue May 29 2001 - 08:48:04 BST