Dwight Elvey
Veteran Member
I would imagine any fully S100 floppy controller would work...there is a jumper to cut on the motherboard to disable the EX85 boot ROM and you'll need to disable the EPROM slots, and RAM slots on the motherboard. You will need more memory than the 4K from memory; no pun intended. The 64K JAWS memory card was designed to go with the EX85, but I'm sure others would work...I had some 8K 2102 based cards that worked fine, installed in my computer at one point. Yes, I have the schematics for the Floppy-1A but not the build instructions. The board layout is included. Dwight, the 5610 is the boot loader PROM for the board...I don't have a spare and have nothing to read mine with. Without that PROM, there's no point creating a clone of the board. The addressing problems with your switches, is likely to be the switches themselves...many of these DIP switch modules were notoriously unreliable, even back in the 70s and 80s. The 'jumper field' is actually a blank place to install an EPROM such as a 2708 or 2716 instead of the 5610 PROM. The two serial interfaces are for the console and printer...the EX85 SID/SOD console drivers are no longer implemented.
Although, not easy, one can write their own boot loader. It is software and assembly level stuff but not rocket science. I was putting together a NC4000 system. It is not anything like a microprocessor anyone is likely to come upon. It is know as a direct Forth processor. I purchased an old XT flopy disk controller card. I did not look at any software for a PC. I looked at the data sheet of the controller chip used. I wrote low level code to format, read and write the disk from scratch. Once to that point I also wrote code to read and write DOS disk using the older FAT12. I did this all with information found on the web. I wrote all the low level code myself. To say a card is useless without the ROM is only saying you don't have the slightest idea what the computer needs to do. Having a schematic of the card is a large advantage. All I had was the pinout for the PC bus.
There is nothing magic about writing code for hardware. It is worth knowing how things work. The more you know about things the better you'll be at maintaining it. Treating everything like a black box with a locked cover is a poor way to advise others. Learn to open the boxes. Treat each closed one as an opportunity not as a road block.
The EX85 comes with a monitor. It is not like there is no way to experiment. It is what it was made to do.
Dwight