If that homebrew stuff would explode, emulator is easy as pie to make, combine dosbox with fceux. But i doubt that a auxilary non bootsble videocard with composite only output is anything that many will embrace. Better thing to do is make a franken-emulator 80386+NES video. Maybe even add NES cpu for a sound co-processor.

Wow, this is legitimately cool! Question is: What do we do with it?? 😁 Agreed, that if you put a NES CPU on it, we could have something akin to the Amstrad Mega PC but with a NES! That would be soooo awesome!

Very cool, I really like these kinds of projects!

And yes, an "NES on an ISA card" would be awesome, similar to the 3DO Blaster or the NEC PC-FX GA.

TheMobRules wrote on 2025-06-26, 17:50:

Very cool, I really like these kinds of projects!

And yes, an "NES on an ISA card" would be awesome, similar to the 3DO Blaster or the NEC PC-FX GA.

Hi, it reminds me of the Spectravideo SVI-838 (aka X'press 16).
That was an IBM PC with an MSX2 graphics chip and AY-3-8912 sound chip.
It superimposed CGA over the V9938 VDP. Some PC games were ported to MSX2.

https://www.msx.org/wiki/Spectravideo_SVI-838
https://www.rigpix.com/vcomp/spectravideo_svi838xpress16.htm

Edit: What I think would be interesting is to give an IBM PC running DOS the capabilities to tiled graphics, like the NES/Dendy/Famicom had.
It would combine things like files and large hard disk storage with it.
I'm looking forward to a Chip 'n Dale 3! Or a new Mega Man/Rockman. :)

Edit: Now that think of it, the Creative Music System (Game Blaster) would be a fine assistant in the sound departement.
Sure you can go AdLib, too, but giving some of the old PSGs something to do would be nice.
And technically speaking, the CSM chips were part of the original 8-Bit Sound Blasters, anyway. ;)

Edit: Another, funny idea: If we make a simple composite video capture card/parallel port dongle,
we can display the NES PPU image on a VGA card in an overlay window.
I know, it sounds crazy, but such framegrabber homebrew circuits were made in late 80s and early 90s.
To grab composite video from a video camera or a VHS player/VCR/Laserdisc player.
Capturing video instead of still images needs a 486 or Pentium, maybe.
It depends on the resolution of the capture. For NES, it can be low-res.

Hmm.

I wonder if you could route video output from the chip to the VGA feature connector on a given ISA/VLB video card with an internal ribbon cable.

CkRtech wrote on 2025-06-28, 05:00:

Hmm.

I wonder if you could route video output from the chip to the VGA feature connector on a given ISA/VLB video card with an internal ribbon cable.

I think the NES PPU only outputs composite video, so I assume you'd need to integrate something like the NESRGB to the design and make it work with the feature connector. But I'm not an expert so what I say might be completely wrong!

^The French NES used to have a SCART lead for the old French TVs of the 1970s/1980s.
So it did provide RGB, rather than Composite. If memory serves, the RGB was generated from PAL signal.
The conversion was made by a single IC, I think. Sony V7021?

http://blog.hardcoregaming101.net/2009/12/fre … rgb-output.html?

Edit: Using an interposing circuit for CGA/RP2C02 PPU would be an option, too.
Both use NTSC at 60 Hz, at LD resolution (240p)..
That's how the SVI-838 had worked, in principle. Both video chips could output same time.
The CGA card is useful for text output, for example. For in-game dialogues.

Edit: Using a simple switch is also a possibility, of course.
Many PC CGA users had an ordinary video monitor attached to CGA card.
Either for Composite CGA with artifact colours or because they had a monochrome monitor.
Green and amber monitors were not uncommon at the time.
Even C64 users used to have them as an upgrade from TV w/ RF input.

Edit: Anyway, I was just thinking out loud. Never mind. 😅

btw kagura1050 - Thanks for sharing your work with us and good luck in your endeavors with this project.

I'll have to admit that I am curious what sort of system emulation could be managed on an ISA-era machine since the NES PPU would now be available in hardware. A 32k ROM-based cart without bank switching or any other support chips would perhaps be a good starting point after a functional emulator for the NES CPU was created alongside whatever frankenstein glue logic is required. Sound is integrated into the NES CPU, so you would lose that.

You could also convert 6502 assembly to x86 assembly for an existing application and see if you could manage to meet all the timing requirements of the PPU. A native 6502-based game is making the most of that instruction set inside a short period of time. The raw MHz of an IBM compatible PC is nice, but the instruction set versus 6502 is apples to oranges.

Lots of fun, think outside the box possibilities here.

EDIT: Also worth noting that an FPGA clone of the PPU is underway here: https://github.com/andkorzh/RP2C02-7-

A highly clock-accurate FPGA clone of the NES 2C02(7) PPU, created on the basis of reverse engineering.

This design has multiregional timings NTSC | PAL . Color output in RGB888 format.

EDIT: Also worth noting that an FPGA clone of the PPU is underway here: https://github.com/andkorzh/RP2C02-7-

Here basically goes the computing power of a Pentium IV to provide the functionality of an i4004.
😢

It has arrived! However, I don't have the logic IC yet, so it will be a while before I can assemble it.

Build Day 1:
I lost the whole bag of HC573 somewhere.
Also, I didn't have 75 ohms and 820 ohms in the 0805 set I had. Soldering is almost done.

CkRtech wrote on 2025-06-28, 15:53:

btw kagura1050 - Thanks for sharing your work with us and good luck in your endeavors with this project.

I'll have to admit that I am curious what sort of system emulation could be managed on an ISA-era machine since the NES PPU would now be available in hardware.

Thank you! I'm more interested in developing new games for this card than in system emulation. (RP2C02 can only be obtained by dismantling real NES/Famicom consoles, so I think that running the same software would just reduce the number of survivors...)

CkRtech wrote on 2025-06-28, 05:00:

Hmm.

I wonder if you could route video output from the chip to the VGA feature connector on a given ISA/VLB video card with an internal ribbon cable.

TheMobRules wrote on 2025-06-28, 05:19:

CkRtech wrote on 2025-06-28, 05:00:

Hmm.

I wonder if you could route video output from the chip to the VGA feature connector on a given ISA/VLB video card with an internal ribbon cable.

I think the NES PPU only outputs composite video, so I assume you'd need to integrate something like the NESRGB to the design and make it work with the feature connector. But I'm not an expert so what I say might be completely wrong!

Jo22 wrote on 2025-06-28, 06:57:

^The French NES used to have a SCART lead for the old French TVs of the 1970s/1980s. So it did provide RGB, rather than Composit […]
Show full quote

^The French NES used to have a SCART lead for the old French TVs of the 1970s/1980s.
So it did provide RGB, rather than Composite. If memory serves, the RGB was generated from PAL signal.
The conversion was made by a single IC, I think. Sony V7021?

http://blog.hardcoregaming101.net/2009/12/fre … rgb-output.html?

Edit: Using an interposing circuit for CGA/RP2C02 PPU would be an option, too.
Both use NTSC at 60 Hz, at LD resolution (240p)..
That's how the SVI-838 had worked, in principle. Both video chips could output same time.
The CGA card is useful for text output, for example. For in-game dialogues.

Edit: Using a simple switch is also a possibility, of course.
Many PC CGA users had an ordinary video monitor attached to CGA card.
Either for Composite CGA with artifact colours or because they had a monochrome monitor.
Green and amber monitors were not uncommon at the time.
Even C64 users used to have them as an upgrade from TV w/ RF input.

Edit: Anyway, I was just thinking out loud. Never mind. 😅

Yes, RP2C02 is a composite output, so connecting it to the feature connector requires a lot of external circuitry (like NESRGB). There was also a variant with RGB output, but it was only used on a few models. Personally, I think the simple switch method is interesting! It's like "80s Voodoo".

By the way, regarding the software for this card, I think it will almost certainly be DOS-only. This is because the OAM (sprite definition) must be written within 0.1 to 1 milliseconds after the VSYNC interrupt (it will evaporate if it takes longer than that). Also, with the current circuit, the name table and BG definition updates must also be done during the VSYNC period (or the BG display must be disabled during the update). The latter can be solved by adopting a dual-port RAM (which, as a side effect, allows writing outside the VSYNC period), but the former cannot.
Anyway, I will update again when I receive the parts! Thanks!