Rex classic *can* replace the main rom. It doesn't normally but it has the option if you set it up.
It installs into the option rom socket and it's main job is actually to be an on-board option rom library, where you can load up option rom images and switch between them all purely from software. It can also take full ram image backups and restore them, and finally it has two special blocks of memory for main rom images. In order for the rex to take over the job of the main rom, it needs the rom image loaded into it, and the /CS signal line for the main rom run out to a pin on the rex so that when the motherboard calls for the main rom to be active, the rex can respond instead. Just read the docs on bitchin100 and tandy.wiki about it. REX# and REXCPM don't offer the feature so there is no other really convenient way to hack on the main rom. You have to open the case repeatedly to actually remove the rom, or run some kind of janky ribbon cable to an external socket. Unless you count VirtualT, but then you are debugging getting a rom to work with an emulator not with the hardware. I have to say, if I had paid Steve for a classic rex as many people have by now, I would be pretty upset at hearing "It has bugs I know about but I'm not going to fix." My 2 cents as a user. Steve, would you consider describing the bugs and making the sources available for the several binary blobs that rex classic currently relies on, so that someone else can fix what you don't want to? For one thing, a totally different issue, I have wished I could fix the tpdd routine in the installer that seems to have changed in some way after build 162. It's inarguably broken, proven by the simple experiment that it doesn't work with a real tpdd. Right now the situation is, you won't fix something, and you won't let anyone else fix it either. Can you possibly see how that might be just a bit frustrating for a user? -- bkw On Sat, Dec 19, 2020, 6:35 PM Scott McDonnell <mcdonnell.j...@comcast.net> wrote: > Will do. Just so I understand, the Rex replaces the main rom? The M100 > will boot directly from the Rex? And with the Rex, I can customize my own > applications, autolaunch, etc? This goes into the DVI socket on the bottom? > > > > I had looked at it before, but the descriptions seem to be written for > people that are already well into the Model 100 and not very clear to a > TRS-80 newbie like me. :) > > > > What I would like to be able to do: > > Replace the main ROM > > Custom menu > > My apps not stored in RAM dependent on battery > > Autolauch a program at power on (and preferably be able to exit out to > menu if wanted) > > Ease transfer of files back and forth with a PC (TPDD emulator or > Trashtalk) > > > > Thank you to everyone that has replied. > > > > *From: *Stephen Adolph <twospru...@gmail.com> > *Sent: *Saturday, December 19, 2020 6:27 PM > *To: *m...@bitchin100.com > *Subject: *Re: [M100] Model 100 Repair - Keyboard not responding,LCD > missing a column > > > > Scott, I recommend before you jump into a REX solution that you read my > REX# and REXCPM wiki pages at Bitchin100. > > REX Classic is the DIY option, but I no longer support it, and it has > known defects. > > My 2 cents as the designer... Steve > > > > > > > > On Sat, Dec 19, 2020 at 6:12 PM Brian White <b.kenyo...@gmail.com> wrote: > > Actually with rex classic you don't even need any rom in the main rom > socket so you don't need any of those boards, just a single wire from the > /CS pin in the main rom socket out to the REX. You just can't run the > machine *without* the rex after that without opening back up to put a rom > back. The flexrom board just lets you install or remove the rex at will, as > well as being re-writable itself by being a 28C256. > > > > On Sat, Dec 19, 2020, 6:04 PM Brian White <b.kenyo...@gmail.com> wrote: > > > > On Sat, Dec 19, 2020, 2:38 PM Scott McDonnell <mcdonnell.j...@comcast.net> > wrote: > > Now that I have proven out that a 27C256 EPROM is working fine in this > one, I am going to play around with customizing it. The real ULTIMATE would > be to replace the ROM with an EEPROM (like 28C256) and add in some type of > loader where you could update the main firmware over serial. That may not > be possible because often in these 80’s computers they usually placed some > IO address space in the ROM area (since write is not possible to the ROM) > and decoded it using the write signal and address. It was a simple trick > for accessing output only IO. I am talking out of my rear end right now > because I haven’t studied the schematic/memory map in detail yet. > > > > http://tandy.wiki/FlexROM_100 > > > > http://tandy.wiki/FlexROM_102 > > > > Especially in concert with REX Classic > > > > http://tandy.wiki/Building_a_REX > > or > > arcadeshopper.com sometimes has rex classic pre-built you can just buy. > > > > You'd use the FlexROM_102 in the 100 that has the standard pinout. > > > > If you don't care about using the fully software loadable main rom via > REX, and only need a plain 28C256 to 27C256 adapter without the /CS > breakout remote loop, this would be a bit more convenient because it > doesn't need a soic-28 test clip to program it. > > > > http://tandy.wiki/28C256_to_27C256 > > > > You just switch a couple jumpers and pop the board right in the programmer. > > >
