Overclock demo

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tepples
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Joined: Sun Sep 19, 2004 11:12 pm
Location: NE Indiana, USA (NTSC)
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Overclock demo

Post by tepples » Sat Mar 14, 2015 7:09 pm

Do you like to overclock your NES? Run this ROM and see how far you're pushing the CPU. And if you've figured out how to change the clock while the power is on, be even more amazed.

This is part of the NES POST project.


EDIT: It has come to my attention that the way I'm figuring cycles per line has some systematic error due to FCEUX sucking at timing when the 9 sprites bit is activated. I have updated the ROM.
Attachments
oc-r1a.zip
With corrected sprite 0 trigger horizontal position
(24.41 KiB) Downloaded 1215 times

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l_oliveira
Posts: 402
Joined: Wed Jul 13, 2011 6:51 am
Location: Brasilia, Brazil

Re: Overclock demo

Post by l_oliveira » Sat Mar 14, 2015 9:20 pm

Machine has a Brazilian M-PAL clone discrete PPU (same timing as NTSC but outputs color information in PAL standard), UM6548, clocked at 21.453666Mhz(3.575611Mhzx6).

@29.498928Mhz:
Image
Dendy-esque UMC CPU

Image
Legit RP2A03E


Using the legit RP2A03E CPU with the NTSC clock:
Image

With M-PAL clock:
Image

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Eugene.S
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Re: Overclock demo

Post by Eugene.S » Sun May 03, 2015 5:08 am

Dendy (6527P/6538 chips):

Image

So, this old researches by HWM are confirmed again.

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