The motherboard can support 40 or 80 columns. 80 columns is probably best for business applications, but is not so good for games – and most people like games.
The following steps were required:
- Move all links – there are three sets. The instructions are on the PCB assembly diagram.
- Remove the extra two video RAMs. It can’t cope with the extras being present in 40 column mode. I learnt this by experiment.
- Change the Edit ROM to a 40 column ROM (now just a link on a EPROM adapter).
I’ve put in an EPROM that can hold both 40 column and 80 column ROMs.
The ROM situation is a little complex. The 4016 has 7 ROM sockets designed for 2332 ROMs. The Edit ROM is at UD7, but out of the factory is a 2316. The 2316/32 ROMs
These ROMs have a no ROM feature so they can be disabled. The machines that I have use some 2532 EPROMs. These don’t have the disable feature, but are otherwise pin compatible with the 2332 sockets.
The problem is that 2532 EPROM are somewhat uncommon and are complex to program. I don’t have a machine that can program them. The closest replacement is a 2732 eprom that is available and that I can program.
They are close but not identical to the 2532. Fortunately, a kind soul has designed a small PCB to adapt them.
https://github.com/SukkoPera/Open2327RomAdapter
This adapter can be configured to replace either 2364 or 2332 ROMs. A larger EPROM can be used on the adapter and images selected using switches.
I’m not sure why the designer didn’t add a pin for A12.
I opted for the over-the-top 512. They are easy to get and have been tested.
A link between pins 1 and 2 is an easy way to select between images at either 7000 (link on) or F000 (link off). I put the 80 column ROM at F000 and the 40 column ROM at 7000.
For the 40 column ROM, I used edit-4-40-n-50Hz.901498-01.bin.
