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Hey I recently won myself a playchoice pcb and I've been thinking about rgb modding my av famicom. I was wondering if I can rgb mod it the same way people rgb mod their nes or if anything different is required. I've been looking for a pinout of the famicom ppu but so far I've had no luck

The Famicom PPU is identical to the NTSC NES PPU.

tepples wrote:The Famicom PPU is identical to the NTSC NES PPU.

Right'o. You can put the RGB PPU in any Famicom or NES, as the PPU is pin compatible between the following:

HVC-001 - the original Famicom
HVC-101 - the New Famicom (A/V)
NES-001 - the original ‘toaster’ NES
NES-101 - the NES2 'top-loader'
AN-500 - Sharp Twin Famicom
AN-505 - Sharp Twin Famicom II
Famicombox
Sharp 19" NES TV
AN-510 - Sharp Video Titler
C1 series from Sharp
VS. System Arcades
Playchoice-10 Arcades
Some (non-NOAC) clones; Dendy comes to mind.

There are some differences though... The AN-510, Sharp C1, Playchoice and VS. Systems all have RGB PPUs, as may the Sharp NES TV for the US market,, however VS. System PPUs have differing colour sets to prevent easy piracy.

Very early HVC-001 PPUs have a design flaw that makes them unreliable, and it's possible that early PPUs will have trouble with some mappers.

As I recall, the NES-101 PPU also has glitches that cause video errors and make A/V output problematic.

Also note that a handful of games don't run on the RGB PPU, so you may want to consider wiring both an RGB and an NTSC Composite PPC in series, on a daughterboard with selector switches.

That way, you have a fallback for non-RGB compliant games.

I wonder if any of the older clone system PPUs are RGB...

I never tried screwing around with them to find out.

It may also be possible to design an FPGA replacement PPU that handles RGB output *and* correctly handles the games that Sharp's chip doesn't like.

If you rip a chip from a VS. System, you can probably get it working too, but you’d need to be more creative.

Frankly, I think it’d be cooler idea to modify a Playchoice board to accept NES/FC carts. I should hunt down some PC and VS boards to muck around with and add a cart slot to them, inside a cabinet and make a PowerPak arcade.

Huzzah! One more project to attempt!

-Xious

Written on my Treo 700p in Blazer.

ahh fantastic! Thanks so much for the help

I'm using a hvc-101 so I don't think I'll have any issues with reliability

If the NES PPU is identical to the Famicom PPU, then why was Blargg having trouble getting OAM data reading to work?

Dwedit wrote:If the NES PPU is identical to the Famicom PPU, then why was Blargg having trouble getting OAM data reading to work?

AFAIK, they are just different revisions. They are still pin-compatible though, and that's all that should matter for the OP.

tokumaru wrote:

Dwedit wrote:If the NES PPU is identical to the Famicom PPU, then why was Blargg having trouble getting OAM data reading to work?

AFAIK, they are just different revisions. They are still pin-compatible though, and that's all that should matter for the OP.

yeah I just wanted to make sure they were pin compatible excluding rgb and sync.

Also I'm not planning on playing a large library of games. Of course I'm gonna install a socket so I can swap ppus easily. I hope that the composite ppu doesn't need the ground connections that're rgb on the playchoice ppu. I also heard that the sync pin from the rgb ppu goes through the same connection as composite video so I'm assuming I can leave that connected to the famicom pcb

and I wouldn't want to use a clone ppu I'm really big on collecting/using original hardware even if it's modded which is why I'm going with the playchoice. And yes I agree that modding a playchoice to accept famicom/nes carts would be awesome but the playchoice pumps out inverted colours that requires an extra circuit from what I read (lazyness). Also I really like the look of my AV famicom and would hate to have to retire it for a massive playchoice pcb wired through my supergun.

Also about your little project idea here...even if you build a cart adapter to playchoice (I bet you could sell those for a nice profit) you may have the same problem with it not accepting the complete library of console games. The playchoice system has a fairly limited library of available games. So who really knows exactly how compatible that platform is with the entire nes/famicom selection

I've found some mods that apparently make 99% of the library work no problem on a rgb modded console so once I get the ppu installed and working I'll take a look at adding those little tweaks.

Dwedit wrote:If the NES PPU is identical to the Famicom PPU, then why was Blargg having trouble getting OAM data reading to work?

I also raised this point back then but had no answer. There is definitely something wrong about what Blargg said (that OAM was readable on the NES and not on FC). The most likely thing is that the's got a different PPU revision in his NES than in his FC - and that OAM is readable on newer PPU but not the older ones or something like that.

I'm also curious, does the dual moniter playchoice use the same ppu for both screens? I wasn't able to find a closeup picture of the pcb anywhere but from what I saw it looked like there's only just 1 rgb nes ppu on the dual moniter pcb.

It looks like the secondary monitor is run exclusively by the Z80 timekeeping CPU.

Drakon wrote:I'm also curious, does the dual moniter playchoice use the same ppu for both screens? I wasn't able to find a closeup picture of the pcb anywhere but from what I saw it looked like there's only just 1 rgb nes ppu on the dual moniter pcb.

The second video generator is made completely from TTL chips, mostly 74LS161 counters, multiplexers and 74LS166 shift registers. It's the way most arcade games before 1986/87 were built.

Would it have been cheaper to just stick a second NES in there?

Perhaps the menu developers liked the Z80 better than the 6502. Or perhaps it was designed by the people who made Punch-Out!!, which also used a dual-monitor setup and a Z80 for game processing. Or perhaps it was made obscure for copy-deterrence reasons.