Comos Cop (from Caltron 6-in-1) hangs on SOME CPU+PPU

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krzysiobal
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Comos Cop (from Caltron 6-in-1) hangs on SOME CPU+PPU

Post by krzysiobal »

There is a game "Cosmos Cop" from the "Caltron 6 in 1" multicart. It works fine on Dendy CPU+PPU
title.jpg
dendy1.jpg
dendy2.jpg
However, when used in NTSC timing console, title screen shows normally, then the intro shows and when the main game starts, it just hangs.
One time i was able to start it, but all the water was black and the game hanged finaly after a couple of seconds:
Another weird thing is that on this NTSC console, the narration text at the beginning is white, not blue
fc1.jpg
fc2.jpg
So I thought - maybe the game tries to read-back the palette or OAM and it fails because this UA6528 PPU can't do that, but the game does not seem to do that. I blamed the PPU, but on my test console, where I can individually toggle one of two CPUs (Dendy/NTSC) and PPUs (Dendy/NTSC) separatelly, it looks like this

Code: Select all

CPU   | PPU  | Game
------+------+-----
NTSC  |NTSC  | hangs (text is white)
Dendy |NTSC  | works (text is blue)
Dendy |Dendy | works (text is blue)
NTSC  |Dendy | hangs (text is whit)
so looks like the CPU is culprit. I guess why.
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Gilbert
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Re: Comos Cop (from Caltron 6-in-1) hangs on SOME CPU+PPU

Post by Gilbert »

Just a wild guess. If CPU is the culprit, will whether support undocumented instructions (or a working decimal mode) or not a possible cause?
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Individualised
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Re: Comos Cop (from Caltron 6-in-1) hangs on SOME CPU+PPU

Post by Individualised »

I'm under the impression that only very early clone chipsets support decimal mode. Is this true?
NewRisingSun
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Re: Comos Cop (from Caltron 6-in-1) hangs on SOME CPU+PPU

Post by NewRisingSun »

There is a single known clone CPU supporting decimal mode: GS870007, mounted in the earliest Bit Corp. famiclones.
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