Sunday, November 1, 2020

Core Memory "Modern" Replacement (for Data General Nova, DCC D-116, Etc)

WARNING:  The below memory card will work ONLY in the "Classic" Nova, but not in Nova 1200 or newer models.

Upon one of my several visits to the Living Computer Museum in Seattle (back in 2019, before they closed permanently because of COVID...), I became quite fascinated with the "not-so-core" memory board in their Data General Nova on display.

The above 2 images were stolen from
Below images were taken by me.
Well, I decided that this was just TOO cool, and since the LCM was all about sharing and preserving, I managed to find the museum staff engineer who developed and built this board.  His name is Jeff Kaylin.  He was very kind and generous, not only of his time to talk to me about it, but he actually emailed me the schematics and his EAGLE PCB design files for this.

Now, you notice that he has some very obvious (and artistic) "reworks" on this board, with added chips upside-down with wires.  His colleagues told me initially that he did that on purpose, to demonstrate what would often need to be done in vintage board development.  I of course asked Jeff about this, and he said that they were being generously gracious with their replies, but indeed, it wasn't intentional.  This was his oversight that he only recognized when assembling the board.  He needed the inverse signal (high vs low) on these leads, and had to install these chips as the "inverters".

So, armed with all that knowledge and his files, one year later, we've "upgraded" Jeff's design, and are building that here. 
And, because you cared enough just to read this far, you can download our work right here, and build your own:

All we ask is that you 

1) do good things with it, and 

2) let us know here what you've accomplished, by clicking on the Contact tab and emailing us.

We are hopeful that this project will help us (and others) avoid future moments like this one:

Data General Nova Keronix Core Memory Board 74S03N chip gloriously releasing magic smoke


And, just for reference, here's an original schematic for an 8k core memory board for the DG Nova 800, hosted by, thank you very much bitsavers! 

The "Original" 1968-1969 Data General Nova Backplane Map, courtesy of Legendary Bruce Ray!

Note the difference between that and the 800/1200/1210 backplane:

The Data General Nova 1200 Backplane Map, courtesy of QuantX.

And another version of the The Data General Nova 1200 Backplane Map, courtesy of tnthalls.

This logic should be the same, although, obviously, no ferrite cores being used here.

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