nesdev.org

https://www.youtube.com/watch?v=2_rCGmTrLsk

This seems to be a ROM hack of SMB1 for an overclocked NES; more like a fantasy console.

Where is its datasheet? I actually have a ROM like this (some old version), and I'm not sure how the heck these extra addons have been made.

But the graphics and everything are amazing! Look at 3:44 and 2:14. I cannot believe this. It's amazing...

This made me recall my own daydreamed HRES (Homebrew Retro/Refugee Entertainment System): viewtopic.php?f=5&t=18036

So, is there a way to implement this? I actually own a Teensy 3.5 development board with an ARM microcontroller on it. It has a great Arduino interface. I also have an 8-bit parallel (8080-style interface) LCD from Adafruit model ILI9341 which means I could assemble an actual "emulator" of this fantasy console.

Parallax layers? This is an emulator hack.

Specifically apparently a hacked copy of Mednafen.

Other than parallax, this isn't too far out of line for what the VT03 (and newer) can do, but that's 1- only available in chip-on-board, and 2- always uses their multiplexed "OneBus" ROM interface

If I had the time (and the graphic art talent), I would create a VT03 ROM hack of SMB1 to see how close I could get it to look like the Super Mario Allstars version.

Or.. you know.. hack the original SMB hack to run on a PC-Engine for bigger sprites, more color, more ram, four time the speed.
https://www.youtube.com/watch?v=5i48xMQX7NI <- Megaman NES rom running on the PC-Engine with a few sprites upgraded (color and size).
Or the PC-Engine Supergrafx with even more sprites and BG layers haha.

I have debated modifying one of my NES's to reroute the PPU EXT pins to the extension pins on the cartridge port. Could be possible to achieve something close to this by doing that and slapping on a micro processor into the cartridge to act as a virtual secondary PPU.

Parallax, yes. Full 16-colors for that parallax layer, yes.
But, the sprite and PPU background layer drawn by the 2C02/2C07 would be unchanged. The PPU's native background layer would share colors with the parallax layer, and both sprites and background would always be on top of the parallax layer.

On the 2C02, I'm pretty certain the EXT pins would let you draw a (severely overscanned) 282x242 picture. 2C07 would be restricted to the same 252x239 that the PPU itself emits.