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The Speed Rumbler (srumbler) wrong clock speed/Aspect ratio #7930

@jotego

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@jotego
Contributor

Hi,

I have measured the M6809 and Z80 clock frequencies on an original board. Find the scope snapshots attached. The M6809 EXTAL is set at 8MHz (vs 6MHz in srumbler.cpp) and the Z80 clock is 4MHz (vs 3MHz in srumbler.cpp)

EXTAL 6809
Z80 clk

The base crystal is 16MHz, so the frequencies of 8 and 4MHz make sense
imagen

The M6809 is halted while the sprite buffer is copied (130us, this reduces the effective speed of the CPU). The halt process is likely to be triggered by the CPU with a write at a given address, like in other CAPCOM games of the same era.
Halt width

Finally, the aspect ratio looks quite different when coming out of the PCB
imagen

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happppp

happppp commented on Apr 5, 2021

@happppp
Member

According to cabinet photos, the aspect ratio is similar to MAME.

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          The Speed Rumbler (srumbler) wrong clock speed/Aspect ratio · Issue #7930 · mamedev/mame