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mg_notes:iie_card:weird_stuff [2018/12/21 17:48]
M.G. [Weird Beep]
mg_notes:iie_card:weird_stuff [2018/12/21 17:53] (current)
M.G. [Slot Scan Scam]
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 The $02 $03 sequence behaves as if CMP #$C0 or CMP #$Cn-1 has been executed and if it has, displays "​UNABLE TO BOOT FROM STARTUP SLOT" in the center of the screen in a similar manner to the copyright message. ​ The message is not in Apple II memory. ​ It returns with the flags set as executing the CMP instruction would have. The $02 $03 sequence behaves as if CMP #$C0 or CMP #$Cn-1 has been executed and if it has, displays "​UNABLE TO BOOT FROM STARTUP SLOT" in the center of the screen in a similar manner to the copyright message. ​ The message is not in Apple II memory. ​ It returns with the flags set as executing the CMP instruction would have.
  
 +My ''​iie.card''​ [[https://​github.com/​mgcaret/​davex-mg-utils/​blob/​master/​iie.card.s|utility]] for Davex can exploit this to determine which slot is configured for startup via the [[https://​github.com/​mgcaret/​davex-mg-utils/​blob/​master/​iie.card.s#​L118|dispslot routine]].