Ohio Scientific 440 Video Board

[CommodoreZ]

Recently at VCF East, I purchased a pair of OSI boards: a 440 video board, and a 420c 4K RAM expansion. I've seen references in the documentation of how the 420c can be used to supplement the memory of the 440, enabling pixel graphics, not just 32x32 text. I've been looking for photos of what 440 board builds look like with that supplemental 420c. I've yet to find a photo of the ribbon cables from the 420c connecting to the 3 empty sockets on a 440 to get an idea of how that might look.

I also noted in the manual that 3 kinds of keyboard can be used, including the Sanders 720 keyboard commonly seen for sale in surplus listings in places like Byte magazine. I'd like to put my 720 to use on the 440, but I was also wondering if anyone had seen such a keyboard installed with this or any other OSI video board before.

I've already asked the OSI forums about it, but figured it wouldn't hurt to enquire in other places in hope of finding photos and information about just such a setup. Here are pictures of the boards in question:

 

[CommodoreZ]

Updating this long forgotten post because it seems my old image links got clobbered, and I can't edit the old post to re-add them. C'est la vie.

I asked around in a few communities that might have seen what I was talking about, and so far I have found all of one example of a 440 connected to a 420. Seems the Challenger 65V in the DigiBarn collection is configured to this end:
https://www.digibarn.com/collections/systems/challenger/page_01.htm You can see it best in an image on page 2, note the 3 ribbon cables jumping between the two rear-most boards, and how the 420 board isn't populated with a full complement of Molex bus connectors because it doesn't need all of those signals from the bus to do its job.

Either way, I'd rather not tear up the 420 to do this job, as it would require significant removal of components which would be a travesty to do to a perfectly working board for the sake of 2K of RAM. I do intend to try to replicate this functionality for my 440 using a 6116 equivalent and the 2 glue logic chips that seem to be required. The hard bit is working around how the 2102's of old had a separate input and output pin, but I'll give it a shot.

In the meantime, I did get a glitchworks replica 400 up and running replica up and running to test the 420 and 440, combined with a 495 protoboard to bodge in 2K of EEPROM for modern conveniences like EWOZMON. The integration with the Sanders 720 keyboard is coming along, but it's by no means been easy figuring out the subtleties of it all. I hadn't touched the project since the summer when I was making major progress, but I've finally gotten back into it. Still debugging keyboard stuff, and figuring out why the OS65V ROMs don't start reliably yet. I've got more photos of the process here: https://www.commodorez.com/osi.html

So far I haven't found any software specific to the 440's graphics option to show what it can do. Best I could find was one that used the alphanumeric mode in the OSI Small Sytems Journal, Vol 1 No 2, Aug 1977, page 20: https://osiweb.org/OSI-SSJ/OSI-SSJ-V1N2-08_1977_001.pdf