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Re: MAME 0.194 [Re: Vas Crabb] #112519
02/07/18 04:46 PM
02/07/18 04:46 PM
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R. Belmont Offline
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To be fair, knowing what memory location is going wrong could help to backtrace the issue if someone's bored enough.

Re: MAME 0.194 [Re: R. Belmont] #112521
02/07/18 10:35 PM
02/07/18 10:35 PM
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Sydney, Australia
Vas Crabb Offline OP
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Originally Posted by R. Belmont
To be fair, knowing what memory location is going wrong could help to backtrace the issue if someone's bored enough.


Location f68d is in the main CPU's NVRAM - it isn't even close to where the root cause is in the MCU program.

Re: MAME 0.194 [Re: Vas Crabb] #112522
02/08/18 12:30 AM
02/08/18 12:30 AM
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R. Belmont Offline
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Sure, but one could find out where the CPU writes that and then how it determines that the MCU is telling it that. Clearly they didn't have people operating a PCB that gave out free games.

Re: MAME 0.194 [Re: R. Belmont] #112523
02/08/18 01:01 AM
02/08/18 01:01 AM
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Sydney, Australia
Vas Crabb Offline OP
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Vas Crabb  Offline OP
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Originally Posted by R. Belmont
Sure, but one could find out where the CPU writes that and then how it determines that the MCU is telling it that. Clearly they didn't have people operating a PCB that gave out free games.


You'd be surprised - there was an arcade in Wollongong in the '90s that had a Golden Axe machine that gave three credits on power-up. The kids had worked this out and would power-cycle it when the attendant wasn't looking.

Re: MAME 0.194 [Re: Vas Crabb] #112527
02/08/18 03:51 AM
02/08/18 03:51 AM
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LoganB Offline
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Seems like it's a bug with the game?

After zero-ing out that address, it does
Code
038F	ld	a,$01		3E 01
0391	ld	($F68D),a	32 8D F6

Then reads from that address and thus gives 1 credit.

EDIT: nvm. For some reason, the Z flag gets set on the main Z80 the third time it gets to
Code
035E: jr   z,$0368

where it then goes through a few subroutines, the first of which is the one mentioned above. This doesn't look to be an MCU issue, unless the MCU can affect the flags on the main CPU.

EDIT2: Well I'll be darned.
Code
- gladiatr and clones start with one credit due to the way MAME initialises
  memory and the dodgy code the bootleg MCUs use to synchronise with the host
  CPUs.  On an F3 reset they randomly start with one credit or no credits.

Last edited by LoganB; 02/08/18 04:28 AM.
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