Popular Osborne Mods?

[HammysHangout]

I was working on a Osbourne, and found a weird "Reset" mod that was tied to UC15 Pin 19. ( CB2 ).. is there something that the Osbourne looks at on the CB2 pin on reset?

After determining it was just some weird user mod, i actually just removed it.. but i still have another mod that ties into the RTS/CTS lines on the Serial port?

 

[Gary C]

Was it wired as an input to the PIA or an output

UC15 is the video PIA and ports A & B are used mainly for the video port to the memory map and the buzzer and the interrupt from Port B isn't used I think so it would require a mod to the BIOS to make something work as an interrupt?

I know pin 19 can be programmed as an output so it might have been used to throw a reset under program control ?

Its odd though that the reset isn't a real reset and operates through the NMI, pain when it crashes properly and the button won't restart it as I have had occasions when pressing reset has filled the screen with crap and disk writes have damaged the disk image.

 

[HammysHangout]

so, UC15 Pin 19 when to an output of a NOT gate, the input of the NOT gate went to a output of a AND gate, and the one input of the AND gate went to the reset, and the other went to the serial port ... i ended up removing it all.. i didn't see any custom bios in the unit they both looked factory roms.

( the video is up on my twitch.tv/hammy_of_fpf as a vod --> https://www.twitch.tv/videos/1216002523 ) its pretty long.. and im rambling a lot with my viewers.

 

[Gary C]

A quick look through the BIOS 1.3 seems to show that bits 3,4,5 of the B port control are set to 0 which I believe disables CB2 interrupt during the normal initialisation.

So its probably some programmed interrupt routine to do something when something happened on the serial line. What line of the serial port was it on ?

 

[HammysHangout]

I have since removed the mod, i have another osbourne that came in the same lot , when i open it up and see if it has the same mod, I will see if i can see the pin it was soldered to when i install a gotek in bay2

 

[Gary C]

Two Osbornes ?

Snap, they are interesting little machines

My number two has started throwing more ram errors. Going to enhance the test rom to make it more user friendly and turn off the buzzer while it runs.