thanks, see comments below. On Wed, Mar 4, 2026 at 3:09 AM B 9 <[email protected]> wrote:
> Your "long-winded" answer is greatly appreciated! > > Thank you for the tip on removing the REX hook. After hitting ^X at the > MENU, my SPDCHK.DO program is back down to 10 seconds (instead of 11 with > an Option ROM installed). > > I presume you've already tried configuring the CPLD in the MENU hooks and > it doesn't work. Do you recall what the issue was? When I hit Power Off > while running an Option ROM, like T-Word, it always seems to go to the MENU > when I press Power On. Is that not the case with all ROM programs? Could > the problem be that Option ROMs can also hook into MENU and may run before > REXMGR gets a chance to configure things? > Current implementation uses the first timer hook after power up (once M100 OS enables interrupts). The thinking was to be as fast as possible. Is there a MENU hook? I didn't try to use that hook but it would be very late. There is a flag that indicates when MENU is running though. The power up behaviour is controllable by software. So the option ROM designer can define what happens at power up. > > Does the Model T try to continue running Option ROM code when it powers > on, similar to how it continues BASIC? I'm thinking that that can't be > right because then even checking 256 times a second wouldn't be fast enough > for REXMGR to prevent catastrophe. So what is REXMGR racing against? Is it > the hooks that an Option ROM has left in RAM? > yes, it can try to keep running the option rom, and yes even the first timer may not be fast enough. More importantly, in some cases the Option ROMs will auto de-install because from the perspective of the active option ROM, REX ROM is actually installed. This looks like the user has removed the option ROM and installed something else. This can trigger "auto-deinstall" by some option ROMs. > > I know you're reluctant to revisit it, but if you happen to remember why > the standard Power On hooks were unreliable, it might be helpful to others > who could run into the same problem in the future. Could it be that some > Option ROMs use the Power On hooks as well? > I never really bottomed the issue out. To my recollection, I've not seen an option ROM use the power on or off hooks. But they definitely use other hooks. > > —b9 > > P.S. This is probably a silly question, but have you considered using a > hardware interrupt to the 8085 when the CPLD first powers on? > > > The option ROM socket has no hardware hook on the pinout. The goal was plug and play, no wires needed. So, no, I did not try to use a hardware interrupt by the CPLD to the processor on power up. Although that would work great. The CPLD gets programmed on power up automatically and very quickly. It is operational within a very short period of time, maybe even before the CPU comes out of RESET on power up.
