so i got this ms pac cocktail .....that plays reeeeal slow!

kerri369

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so i got this ms pac cocktail .....that plays reeeeal slow!

i fire it up, it goes to the test screen displays ram ok, freeplay ect. ect. then goes to attract screen. i then press player one or two, it starts and plays perfectly except the sound and speed of the game is sooo slow, but plays fine.what gives?
 
If it has a speed up hack on it could one of the speed up things gat reversed or went bad

i am wating for my ms.pac cocktail from my uncel
 
sounds like something wrong with the clock pulse rate to me.....
Chips
3R
3S
2R
2S
they are 74LS161.....
I would start there.
 
Many of the Ms pac's have been sped up so it seems slow if you play a regular one. Is this a dedicated logic board or is it an after market?
 
The speed up chip will only speed up Ms Pac. Everything else is at normal speed and the chip certainly does not effect sound.
 
...freeplay ect. ect. then goes to attract screen.

This is what got my attention. It has to have a modified chip in there somewhere as I thought when the game was set to freeplay, there was no attract screen.
 
the game went into self test then it went into attract screen,starts fine but sounds and speed are slow. dedicated board with no modifications!
 
i wonder if anything is here...
http://lawnmowerman.rotheblog.com/

what supplies the clock signal for the board anbody know? mabye that circuit was modified or mabye that chip that supplies the clock siggy is bad.

You might want ot check the power upply of the board just to make sure the board has proper voltage to the chips.
 
Last edited:
It's funny to see all the people here who really don't know what they're talking about.

The same clock that generates the timing for the CPU generates the timing for the video. If that clock's the wrong frequency, or there's problems in the 74161 counters, it'd affect the video and sync (which is based on divided down versions of the master clock).

The actual apparent "speed" of the game comes from interrupts generated by the VBLANK @ 8C, which is supposed to be at 60 Hz, but if 8C is flakey or if the IRQ enable/disable @ 7K/8k + 8H is flakey or if someone cut the VBLANK line and ran another clock signal in (which was a popular hardware speedup hack), the speed will be too fast, too slow or choppy.

Read the schematics people... there's not much to it.
 
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