Re: [M100] Getting a DVI up and running

[Randall Kindig]

Ah, gotcha.  I have a working DVI setup and am willing to help in any way I can, but we’re a LONG way apart! :)  Randy Sent from my iPad On Nov 19, 2024, at 6:35 PM, Michael Brutman <mbbrut...@brutman.com> wrote:  Hi Randall - I'm in the Seattle area, slightly north of the city.  It is green and lovely up here, but a little wet and dark at this time of the year. Royce, My understanding is that Teledisk should be usable for creating the boot diskette.  During the writing process it detected that it was a single sided image.  I don't have other Tandy hardware nearby, but I do have other IBM PC type machines.  Should I try a specific version of Teledisk or use a different machine to create the diskette? (I'm thinking of using Teledisk to read the image back and compare it to the original image file to eliminate a completely bad disk.) I'll probably setup the o-scope this weekend and monitor the signal lines on both the M102s and the DVI, just to ensure the waveforms are somewhat reasonable looking.  That would help me determine if I have damage or other problems, like bad capacitors. I kind of hate replacing capacitors unless I know they are bad.  Maybe it is my terrible soldering skills, but it's so easy to damage something while trying to fix something else that isn't totally broken. ;-0  I will have a look to see what condition the capacitors are in though. It's a shame the DVI doesn't have a basic serial port or some form of POST display.  It would be so much easier to debug if I could snoop in on what it was doing. -Mike On Tue, Nov 19, 2024 at 1:47 PM Royce Taft <roycet...@gmail.com> wrote: > * The disk I wrote might be crap.  I used Teledisk v2.16 on a 386 PC with a real floppy controller.  It's good enough to load the initial sectors, but I can't verify the rest of the disk.  I might be loading bad data into the DVI buffers and passing it onto the M102, and that could be causing the crash.  But there is no easy way to prove or disprove that. Once the boot sector is read into memory, the DOS IPL takes over and tries to read the next sector (sector 2). IIRC, there is no fault handler for failing to read the next sector. It will just loop trying to read that next sector infinitely, maybe with some delay between tries. I’m only about 75% sure of that as I haven’t spent much time staring at that portion of the disassembly yet. Obviously your DVI is long past this point in the process. I only bring this up to explain my suspicion that perhaps there also isn’t a fault handler for reading sectors for setting up the M100/102’s disk basic. So possibly your boot disk isn’t quite right. This probably won’t have an effect since the DVI appears to read the first few sectors properly, but it wouldn’t hurt to clean the disk drive’s head if you haven’t already. I doubt the DVI itself was damaged by the cable being incorrect. There are buffer/transceiver ICs in the DVI interfacing the M100/102 cable to the DVI’s PPI IC. I imagine those ICs are still working since the M100/102 reads and writes data to tell the DVI to send disk basic, and your DVI seems to be responding to the request at some level. It could be possible there’s some other internal problem with the DVI.  I would lend you mine for testing, but I’m located in Northern California (a couple hours north of Sacramento). I would recommend replacing the capacitors in your M100/102s sooner than later. My M100 worked and looked great, and I could see only a small amount of leakage around some of those tiny capacitors.  Once I started removing them and cleaning the PCB did I see the extent of the damage. I had to run some bodge wires and do some creative capacitor lead routing to accommodate for the lack of suitable through holes for soldering in replacement capacitors. I was surprised when the system worked on the first try after coming of out capacitor surgery. It was pretty ugly. Royce