anetanel wrote on 2021-09-05, 07:14:Could it be that the floppy in only readable in this "bios recovery" state?
Just to confirm: I made a test run of this in an emulator with SvarDOS boot floppy (comparing recovery mode boot against a normal boot).
You're right, it looks like the recovery mode sets the floppy in readonly mode. That's a bummer 🙁
anetanel wrote on 2021-09-05, 08:40:Another observation. While poking around the BIOS Flash with a multimeter while the chip was out, I noticed that the VSS pin (1 […]
Another observation.
While poking around the BIOS Flash with a multimeter while the chip was out, I noticed that the VSS pin (16) is kinda shorted with pins VDD (32) and both NC (1, 30). And by kinda, I mean that the multimeter beeps for about a whole second, and then stops.
I tried doing the same on another motherboard that uses the same Flash (SST29EE010) and this phenomena is not occurring there...
I measured the resistance between VSS and VDD on the "Good" board, and it was about 0.8 Kohm, while on the "Bad" board it is only about 0.08 Kohm. I'm not that good with electronics, but could it be that some other capacitors are at fault?
I also noticed that when testing continuity between the two legs of various capacitors on the board I get sometime a similar behavior - a short beep (not as long as with the Flash socket) and then it stops.Chip datasheet: https://www.mouser.co.il/datasheet/2/176/71061-1102136.pdf
Not sure this helps, but the short beep could just be the capacitors charging up. They start out low resistance, then gradually go open circuit as they charge up (for a constant voltage). I guess your multimeter beeps when current flow is over some threshold, so it'll beep to start with, then stop. How long it beeps for will depend on how much capacitance there is, and what the leakage is (and 80 ohms sound quite high leakage, but I don't have much experience).