Epson PC-486GR: drive select light strobing (PWM frequencies, makes LED seem dim; get brighter when read/write attempt made)
wyatt8740 opened this issue · 2 comments
Hi, I have an Epson PC-486GR (PC-9801 compatible). It has two Canon MD3541G drives, which have 26 pin ribbons, and are attached to adapter boards with 5 1/4" card edge connectors.
I see on this site a pinout for the drive, but it also states that the adapter board (which I have) should adapt it to the basic pinout of the NEC FD1231T.
I compared the pinout to the shugart pinout and I see that they are nearly identical - but when I connect my gotek/flashfloppy to the PC the green LED strobes so fast that it looks like the light is steadily on, but dim. I have poked my oscilloscope at it and seen that it's definitely being fed a square wave. This happens with either S0 or S1 jumped.
The machine does not boot from the gotek, although the activity light does for a fraction of a second turn solid green when the memory test is finished, right around when I'd expect the computer to try to check the drives for bootable floppies. Then it goes back to PWM-strobing as usual.
Am I doing something stupid/making some oversight that has an obvious answer to you?
Thank you.
I later fried one of my two goteks while probing the other pins, but I still have one working one, so I can test things if needed. Kind of bad at using an oscilloscope, but I can try to use that, too.
@Pawlicker (who made PR #779) seems to have the same model, and it is sort of implied that they got it working, so I'm going to mention them here. Sorry about that.
Figured it out. Reset all the BIOS software dip switches in the PC to defaults ('hollow' circle positions in settings - some had been changed by prior owner), used shugart interface on Flashfloppy, then flipped one of the DIP's - FDD 640 KB モード (FDD 640KB mode, DIP SW3-2) to ON. might need to set pin02=ndens to fix that. Not tried yet.
Also set base system clock to 8MHz but I don't think that has anything to do with it.
Drive activity light still behaves very strangely. Any idea what that could be all about?
In any case, closing the issue.