Re: [M100] Getting a DVI up and running

[Royce Taft]

Along the same line, I’ve been thinking of reverse engineering the DVI’s firmware (BIOS) and software (DOS which is loaded into RAM by the BIOS) to the extent that it could be modified to utilize the second side of a disk once the drive is changed out for a double sided one.  I’m fairly certain that the side select signal on the floppy interface is connected to a latch IC used for various system controls. If that’s the case, the single sided drive limitation is one of firmware/software, not hardware (besides the disk drive itself). I say I’m only fairly certain since the schematic is very difficult to read.  The scan of the service manual floating around in various repositories is not exactly high resolution, which makes the schematics practically illegible. There is a user in the Tandy discord who is planning on scanning the schematics from their copy of the service manual this weekend.  It would be a fun project to gain a little more exposure to Ghidra, especially with “overlays” in the memory map such as the memory banking scheme used by the DVI and the region of RAM which will contain DOS once the disk is read at boot.  Royce Sent from my iPhone On Oct 26, 2024, at 14:11, Michael Brutman <mbbrut...@brutman.com> wrote:  The GoTek is a great idea.  I saw a matching TEC drive on auction but it was far too rich for my tastes ..  $200.  It would be nice as a spare, but not at that price. I was also doing some reading and I didn't realize that the DVI was basically a small computer in its own right.  It has a Z80 clone for a CPU, 4K of RAM, some ROM, the video memory, and the character ROM.  I'm almost thinking that I want to reverse engineer the boot code on the diskette and then start making alterations to have it do unnatural things. :) Mike On Fri, Oct 25, 2024 at 9:18 AM John R. Hogerhuis <jho...@pobox.com> wrote: On Fri, Oct 25, 2024 at 9:16 AM Gary Wilkinson <gpwilkin...@hotmail.com> wrote: Another boot option, or an additional project for when you have the DVI running, would be to add Gotek floppy drive emulator to that spare 5.25” slot. The excellent guys in this group helped me get mine working. It now boots from the Gotek. What can I say, but... bitchin'! -- John.