Floppy Connecting
Success! Kinda. I had to make a couple of modifications to get a floppy drive plugged in:
- The pins on the floppy header on the main board are a good bit shorter than typical 0.1" headers, so they did not reach far enough into my floppy cable connector to make contact. I had to sand about 1mm (0.050") from the connector face, and it now just barely makes electrical contact.
- Of my several floppy cables (yes, I have several; don't judge), all had pin 3 blocked. The main board's header did not, so I had to trim off pin 3 so the connector would mate. The odd pins on floppy connectors are all ground, so this is unimportant.
- The Digital Power VSL100-401 power supply has four 5-pin connectors on it. These output +5V, +12V, -12V and -5V, plus a single ground. I made an adapter cable that plugged into the +5 and +12V rails, and brought them to a female "Molex" floppy power splitter cable.
 |
| The sanded-down face of the floppy cable, the cut pin 3 of the main board header, and the Rube Goldberg PSU-to-floppy power cable. |
Floppy Loading
Now the machine was getting closer to my dusty memories of mid-'90s PCs. With a working floppy drive, I excitedly inserted an old DOS 6.2 (not 6.22, alas) boot floppy and was able to see a directory of the disk. Hey, let's try that old classic tool, MSD!
 | |||||||||
| MSD.exe (Microsoft Diagnostics), one of my favorite tools in the old days. |
This led to the (attempted) loading old DOS programs and games. WordPerfect seems to work, and a couple of (simple) late '80s DOS games too. Of course, I will have to try Wolfenstein 3D once I get everything working.
Most important to me, though, was the ability I now had to:
- Backup the Flash-based boot environment to floppy
- Copy the various files for investigation/modifications on a Windows PC with things like Notepad++
- Run Edit, MS-DOS' included text editor, with which I could finally make changes to the "config.sys" and "autoexec.bat" boot files.
I REMed out the @ECHO OFF line of autoexec.bat so that I could see more of the file's execution. I didn't want to change too much; one wrong move and I might make the board unbootable from its C: drive, and I'd have no way of recovering from that (yet).
Floppy Booting?
I copied what I thought was a minimal boot environment to a floppy disk and tried booting from that. It churned a while on boot, ticking and tocking around the tracks. Definitely executing the autoexec.bat! Then the drive halted and... nothing. No display at all. Dang.
This began a long and confusing series of experiments that made very little sense. Eventually I got the machine to boot from floppy and show something on a screen, but more often than not, the screen remained blank. Boot configurations that worked minutes before were occasionally unsuccessful.
This Always Happens
Once, while poking around inside the box after another unsuccessful boot, the display flickered and briefly showed an A:\ prompt. What? More poking revealed that the goofy video cable assembly seemed really touchy, but holding it in just the right position would show a display.
A few minutes of continuity testing against the pinouts I made at the beginning showed several video connections were no longer present. Aha! The microscope revealed the faults on the flexible polyimide circuit:
 |
| Both of the traces leading from the pads to the vias are cracked! |
All of my plugging and unplugging of connectors finally resulted in the predictable casualty. I'll have to repair this and re-run my boot floppy experiments.
