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6R6
Registered: Feb 2002
Posts: 244 |
Disabling AR freeze button
Is it possible to disable the Action
Replay freeze function 100% ?
In that case, please enlighten me... :)
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Style
Registered: Jun 2004
Posts: 498 |
Quote: i'd also like krill to explain how ar would freeze with nmi and irq disabled, because i cant see that working ...
Im pretty sure the cart itself drives the NMI line high itself..... Remember, the reason you can disable NMIs is by not acknowledging an NMI, therefore leaving the NMI line low. From what I can tell from the circuit diagram, the AR itself itself drives the NMI line high with a 74LS74 (from memory).
I dont have a problem with this. However, wouldnt this make it impossible to disable the restore key as well?
Or perhaps the AR only drives the NMI line high when you press the button, and then a short while later grounds it again? If thats the case, I cant see it in the circuit.....
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Mace
Registered: May 2002
Posts: 1799 |
If it was possible to disable such a cartridge feature, wouldn't that have been one of the better piracy protections? |
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chatGPZ
Registered: Dec 2001
Posts: 11107 |
not really, it only works if you disable IRQ _and_ NMI (cause then there is no way for the AR to kick in).
a much easier way is however, to sync a timer to the raster, and every now and then check if the timer is still in sync.... if it isnt, then the program has been frozen (and restarted). and this has indeed been done in some games :) |
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Radiant
Registered: Sep 2004
Posts: 639 |
Quoting The ShadowWhy would you want to disable the freeze button on a cartridge. In this modern 64 day, [...]
Curiosity; "can it be done, if so, how"? To give other people something to put their head against? Just for the hell of it? |
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Style
Registered: Jun 2004
Posts: 498 |
Quote: not really, it only works if you disable IRQ _and_ NMI (cause then there is no way for the AR to kick in).
a much easier way is however, to sync a timer to the raster, and every now and then check if the timer is still in sync.... if it isnt, then the program has been frozen (and restarted). and this has indeed been done in some games :)
Have you tested your theory groep? ie, disable NMI and IRQ and try to freeze the program?
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chatGPZ
Registered: Dec 2001
Posts: 11107 |
actually, no...but since what the freeze button does is causing an NMI, i dont feel like doing it either, its obvious =) |
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Frantic
Registered: Mar 2003
Posts: 1627 |
I remember some compo-pic which (by accident, it seemed) jammed the machine after making sure the gfx was visible. Another way to do it perhaps. :) |
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Style
Registered: Jun 2004
Posts: 498 |
Are you really really sure its that obvious groep?
:D
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chatGPZ
Registered: Dec 2001
Posts: 11107 |
yes, how do you think freeze works? |
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Martin Piper
Registered: Nov 2007
Posts: 633 |
Stopping the NMI will stop most freezers from working. Unless the freezer is actually watching the data and address bus and is able to dump the whole of memory. To restore all the freezer needs to do is dump out touched memory, restore CIA, VIC, SID state (it's possible to read the SID for protection purposes for example) and then start the CPU. Such hardware based freezers that watch the internal buses are practically impossible to stop. |
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