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PostPosted: Mon Jul 23, 2018 1:50 pm 
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Joined: Thu May 19, 2005 11:30 am
Posts: 672
The IRQ handler of Sangokushi: Chuugen no Hasha and Namco Classic II:
Code:
   LDA   $5800   ; IRQ Counter High/Enable
   AND   #$7F
   CMP   #$7F
   BEQ   .L1
   NOP
.L1:   (...)
The IRQ handler of Sangokushi II: Haou no Tairiku:
Code:
   LDA   $5800   ; IRQ Counter High/Enable
   AND   #$7F
   CMP   #$7F
   BEQ   .L2
   NOP
.L1:   JMP   .L1
.L2:   
If an IRQ occurs, register $5800 will necessarily be $FF, at least as described in the wiki, so I wonder why check it, and if for some reason it does not have that value, what's the point of executing an extra NOP in the first case, and just freezing in the second case? No other Namco 163 game that I have checked does this.


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PostPosted: Thu Aug 09, 2018 10:58 am 
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Joined: Fri Jan 24, 2014 9:05 am
Posts: 159
Location: Hungary
My first guess would be an odd protection method against possible bad pirate copies of the mapper, or hardware failure?


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