Re: MK14 memory upgrade
I personally only imagined 0000-01FF of the EPROM (The original range of the PROM) being mapped, the main aim being to do away with the need to use those danged awkward bipolar PROMs.
You could provide jumper links or a DIP switch to set the upper address pins so different PROM images programmed into 200H chunks of the EPROM could be swapped in at will - New OS - Old OS - several demo programs - VDU demo program etc.
If including bus buffering remember that the address line buffers would have to be bidirectional as well, as the VDU needs to be able to drive the MK14's address bus when it takes over the buses.
Agree a secondary regulator powered from the same 8V rail as the main regulator would be a good idea.
One caution about the 6116, we briefly had a forum member called Gert who had all but completed his MK14 replica but for the RAM, and I remember him saying that he had tried a 6116 in the meantime but that it had not worked. Unfortunately he didn't explain why, perhaps he didn't get time to investigate before the proper RAM arrived.
As regards the addition of DIN connectors I don't really favour going vertical unless the cards are mounted in a proper rack, so I would ask that one of the pinouts on the memory expansion board be at the rear with the correct geometry for a right-angle DIN connector, and pinned specifically for the VDU, allowing the MK14 board, expansion board and VDU to be laid in a straight horizontal line backwards. The completed VDU board is actually quite a heavy PCB, especially if it has the modulator fitted at the far end.
|