yah I scanned those and it didn't ring a bell yet; I'll keep looking. On Sun, Feb 26, 2023 at 10:02 AM Brian K. White <b.kenyo...@gmail.com> wrote:
> Perhaps these? > > https://github.com/LivingM100SIG/Living_M100SIG/blob/main/M100SIG/Lib-08-TECH-PROGRAMMING/ROMSW.THD > > And a few others right next to it ROMSW1.TXT ROMSW2.TXT ROMSW.ZIP (which > just has a txt in it) > > -- > bkw > > > On 2/26/23 09:22, Stephen Adolph wrote: > > There are some steps you can take to remove the traces of an installed > > Option ROM from RAM, which work for all option ROMs as far as I know. > > > > There is a file in the M100SIG that outlines this but I could not find > > it this morning. If I do I will reply back identifying the file. > > > > Anyhow this is what REX and REX# and REXCPM do: > > > > 1) Initialize the hook table. The hook table is a set of addresses > > used by RST 7 calls in M100/T200/NEC. The addresses are "jump-to" > > vectors that allow software to hook into specific parts of the operating > > system. There are 2 "defaults" depending on the actual hook itself. It > > is pretty straightforward to write some machine code to reset the hook > > table to nominal. BASIC won't do it because you need full control of > > the machine to cleanly change the hooks table. > > > > 2) You want to remove any "trigger files" like TS-DOS(.BA) from RAM. > > You can do this manually, or you could write some machine code to search > > for the trigger file names in the directory, and delete the files. > > This isn't "super easy" because it amounts to de-installation of a file > > from RAM, which means you need to call some specific ROM routines to > > adjust memory pointers etc. > > > > 3) The M100 main ROM always copies the 8 bytes at 0x0040-0x0047 in the > > Option ROM to upper RAM starting at 0xFAA4. T200 is 0xF4D3, NEC is > > 0xF991. This region of memory should be reset to nominal, which is 8 > > bytes of 00. > > > > 4) Reset the upper RAM area used by Option ROMs to hook in. On power > > up, the M100 copies some software from the main ROM to upper RAM. Some > > Option ROMs install their own code there when they install themselves. > > in M100, you need to copy 36 bytes from 0x036F to 0xF602 > > in T200, you need to copy 42 bytes from 0x0372 to 0xEEC8 > > in NEC, you need to copy 42 bytes from 0x0440 to 0xF590 > > > > > > I think that's it. I imagine what would be useful for manual rom > > switchers is to have a little utility that you can run that "cleans out" > > the Option ROM. > > -- > bkw > >
