What are these mods for?

[vtgearhead]

I acquired a C1-P (OSI 600 Superboard) a few years back and have finally found time to dig in. Can anyone tell me what the set of mods in these photos is for?

c1_top.jpg (5.59 MiB) Viewed 4086 times

ci_bottom.jpg (6.81 MiB) Viewed 4086 times

When I received the machine there was a 40-pin ribbon cable hanging out the back leading from that added connector. An interface for floppy controller, perhaps?

[Klyball]

What chips are in those proto sockets

[vtgearhead]

What chips are in those proto sockets

I assume proto to mean socketed positions, from left: LS02, SN7475, SN7475

[vtgearhead]

More information: It's hard to see on the photo, but the bottom row of pins on the header are tied with diagonal runs of bus wire to a row of via holes at the edge of the PCB. Those then connect to various points in the keyboard matrix (?). Again, I'm brand new to the Superboard and trying to learn.

[vtgearhead]

Anyone? Is this on?

[Klyball]

I dont know what it is but it's not for a disk.

If you could make schematic of the connections, then maybe could figure it , kinda hard from a couple of pics

[vtgearhead]

Sure, no problem! I just thought this might be something very common that folks would recognize. I'll trace the circuit out and get back.

[bartleph]

Hi, It looks to me that it is a Bus expansion. There are two ribbons, 1x16 and 1x8, plus a red wire. Could be an address select?? maybe used for an EPROM Programmer or some other memory mapped peripheral.

[Klyball]

It looks like the 8 wire cable goes to the input of the latches and the 16 cable to the output ,the only signals going to the plug from the superboard are the keyboard lines, no data or address. The laches are triggered on board.

[bxdanny]

Hi. Based on the presence of that WeMON chip, also marked Series II and UK 101, I would strongly suspect that the mods have to do with creating 600D-style 48x16 video. I stress that I did not, and could not, make any attempt to interpret the circuits themselves. But without such a video mod, that WeMON monitor would produce a garbage display, so it seems very likely that that is what it is. One latch may be mapped to $D800, with bit 0 of it's output selecting between 24-character and 48-character mode, with the rest of the added circuitry implementing the 48-character mode itself.