I wonder if this is for all the characters in the ROM or just a segment of them?
Boot it up without the disk drives attached so it goes into AppleSoft Basic.
Then type the following:
for x = 0 to 255 : print chr$ ( x ) ; : next x
Then press 'ENTER' and watch the entire character set print out. From this there you can determine if the whole ROM is affected or part of it.
Another test in case some control characters goof this up is to poke each character on the screen. I'm assuming that the IIgs Screen memory map is in the same place as the older Apples, so this should work:
for x = 0 to 255 : poke 1024 + x , x : next x
This will print out the ROM's characters across the screen, if 1024 is start of the text screen location.
Either way, this will show if addressing problem is in part of the ROM or all of it? If it is in all of it, I believe it would be an easier fix as it would be easier to locate as set amount of address lines affected.
Boot it up without the disk drives attached so it goes into AppleSoft Basic.
Then type the following:
for x = 0 to 255 : print chr$ ( x ) ; : next x
Then press 'ENTER' and watch the entire character set print out. From this there you can determine if the whole ROM is affected or part of it.
Another test in case some control characters goof this up is to poke each character on the screen. I'm assuming that the IIgs Screen memory map is in the same place as the older Apples, so this should work:
for x = 0 to 255 : poke 1024 + x , x : next x
This will print out the ROM's characters across the screen, if 1024 is start of the text screen location.
Either way, this will show if addressing problem is in part of the ROM or all of it? If it is in all of it, I believe it would be an easier fix as it would be easier to locate as set amount of address lines affected.