Nabu PC Floppy Disk Controller Reproduction
Several people have asked me about reproducing the Nabu PC Floppy disk controller board even though, at this point, I do NOT have the only original I know of yet working. If you happen to have a Nabu PC with a working floppy disk drive, please let me know. I could use some assistance.
The Floppy Disk Controller board allows the Nabu to utilize an external dual floppy disk drive and boot up CP/M 3. There are disk images with the software on them and I can view the software with other means but at this point, it just does not boot up. If it could boot a local version of CP/M 3, the Nabu PC would be a stand-alone Nabu PC and you could run CP/M based software on it, as long as it supports 40 columns.
To create a reproduction, you need decent pictures. Below are the pictures.
Below are pictures of the Nabu Floppy Disk controller card. It is made up of two cards connected together via ribbon cable. The “FDC Option interface” board connects to ALL four option slots in the Nabu PC. It also needs to have an 8K Version 2 of the EPROM to work. Both 4K (non-floppy) and 8K Floppy versions of the EPROM are posted. NOTE: You have to modify your Nabu motherboard to accept 8K EPROMs if yours came with a 4K EPROM and that is almost all of them.
Here are pictures of the two boards that make up the Nabu PC Floppy Disk controller. Note once again that the small Option interface board connects to all four of the Options slots as pictured here:
The populated front and rear of both boards:
The main Floppy Disk Controller (FDC main) board:
The Floppy Disk Controller Option interface (FDC option) board:
Since I removed and socketed the chips for troubleshooting purposes, here are pictures underneath most chips:
FDC Main board
The FDC Option board has some traces obscured by the ribbon cable. Here is a better picture with the ribbon removed:
To enable the 8K EPROM, you will need to cut a trace on the motherboard located just to the top right of the Z80 CPU and you will have to solder a jumper to the 8K solder point as shown below. This will allow you to use the 8K Floppy V2 EPROM.
A discussion thread for this project is located at the Vintage Computer Federation Forum here: https://forum.vcfed.org/index.php?threads/the-official-nabu-pc-floppy-disk-controller-thread.1241006/
If you decide to tackle a reproduction of this board, please post in the VCFed thread. Please create a user ID, if you need to. This will allow you to see if others are also doing this. Please check there for any updates. If you have any questions about the Nabu PC floppy disk controller, please post in the thread as others will have similar questions and I may have answered them already there.
Good luck and let me know if you were successful!