Recovering the ROM of an IBM 5100 using OCR (among other things)

[Christian Corti]

On Thu, 27 Jun 2019, Noel Chiappa wrote:
>    > From: Liam Proven
>
>    > This is *epic*.
>
> Indeed. I was blown away by the complexity of his technique for reading
> the digits.
>
> I can't believe there wasn't a much easier technique, though, e.g. using a
> logic analyzer and a small program to read through the ROS!

That's what I have suggested him, but he wanted to test his algorithm on 
this project, and all I can say is wow :-)
The "ordinary" way of reading the Executable ROS contents is to put the 
machine into single-step mode and press RESTART. This effectively enables 
access to the ROS contents via the address and data bus on the backplane. 
You then force the upper address bits from outside (it's an open-collector 
bus), i.e. in increments of 1024 bytes, and sample the 1024 byte block 
from the data bus along with the lowest 10 address bits. The caveat is 
that the display controller will be enabled and permanently accesses the first 
1024 bytes of the memory for the screen display.
I had read the contents of my 5110 Executable ROS modules just like Tom, 
but I used normal image post-processing and OCR - all that many years ago 
and therefore with a lot of manual work involved ;-) But that was 
successful at the end and lead to a functional 5110 emulator.

Christian


>
> Perhaps the challenge of doing it his way entertained him, though, like
> George Mallory's famous line about climbing Everest.
>
> 	Noel
>
>