An NES emulator written in Go.
Resources:
-
Nes Development Wiki http://wiki.nesdev.org/w/index.php/Nesdev_Wiki
-
Another nes emulator in go https://github.com/fogleman/nes
Usage:
$ ./nes somerom.nes
Keys:
up arrow = up
down arrow = down
left arrow = left
right arrow = right
enter = start
Q = select
A = a
S = b
Other keys:
~ = speed up emulator by 3x
- = slow down emulator by 0.1
= = speed up emulator by 0.1
0 = set emulator speed back to normal (1)
space = pause/unpase emulator
R = restart emulator
P = enable ppu debugging
O = stop the emulator after each frame, press O repeatedly
Build instructions:
Needs go 1.18 or higher
Install libSDL2, libSDL2-ttf, and libSDL2-mixer, libSDL2-gfx
$ sudo apt install libsdl2-dev libsdl2-ttf-dev libsdl2-mixer-dev libsdl2-gfx-dev
Using make
$ make
Or pure go
$ go build ./cmd/nes
NSF player is an ncurses terminal based music player of nsf files.
$ make nsf
or
$ go build ./cmd/nsf
$ ./nsf somefile.nsf
Log:
6/20/2020: cpu is mostly complete
6/23/2020: The first time the emulator was able to render an image. This is from the Baseball game. It was very exciting to see an image show up, even if the colors are not exactly correct! Mostly the difficulty in getting to this point was understanding pattern tables and nametables.
6/24/2020: The same Baseball game but rendered with colors from a palette derived from the pattern attributes. I think the colors are still wrong here, as other rom's show a lot of dark blue as well, but its a step in the right direction.
6/28/2020: Contra is playable where sprites are kind of rendered, but the background doesn't scroll. This also demonstrates mapper 2, which contra uses.
6/29/2020: I was using SDL to call SDL_DrawPoint on a renderer for each pixel rendered by the PPU, but this ended up making frames take 10-20ms to render, which seems absurdly long for a modern machine (even with software rendering). The reason seems to be that each call to SDL_DrawPoint incurs a runtime.cgocall invocation, which has high overhead. The pprof cpu profile demonstrates this:
(pprof) top 10
Showing nodes accounting for 21830ms, 77.11% of 28310ms total
Dropped 124 nodes (cum <= 141.55ms)
Showing top 10 nodes out of 50
flat flat% sum% cum cum%
14320ms 50.58% 50.58% 19380ms 68.46% runtime.cgocall
1390ms 4.91% 55.49% 1670ms 5.90% runtime.mapiternext
1350ms 4.77% 60.26% 2310ms 8.16% runtime.exitsyscallfast
1210ms 4.27% 64.54% 1210ms 4.27% runtime.casgstatus
800ms 2.83% 67.36% 4320ms 15.26% runtime.exitsyscall
790ms 2.79% 70.15% 790ms 2.79% runtime.wirep
530ms 1.87% 72.02% 1990ms 7.03% runtime.cgoCheckPointer
520ms 1.84% 73.86% 23330ms 82.41% github.com/kazzmir/nes/lib.(*PPUState).Render
490ms 1.73% 75.59% 2350ms 8.30% github.com/kazzmir/nes/lib.(*CPUState).LoadMemory
430ms 1.52% 77.11% 1040ms 3.67% runtime.cgoIsGoPointer
Colors have been fixed, and rendering uses an in-memory []uint32 array, which is uploaded to a texture and rendered to the window using hardware acceleration. 60fps is easily achievable, and at an uncapped NES CPU my machine can render about 250fps.
7/4/2020: Mapper 1 is implemented so final fantasy and legend of zelda are somewhat playable. Scrolling is still not implemented so a lot of the graphics in final fantasy show up incorrectly. Also none of my characters have a weapon.
7/5/2020: Scrolling mostly works. The gif here is smaller and shorter in time to keep the file size low. Both vertical and horizontal scrolling work, as tested with the purely vertical scrolling game ice climbers. There are some remaining glitches with scrolling as walking around the map in final fantasy renders the wrong tiles a lot of the time.
8/18/2020: Audio, scrolling, and tons of other stuff is working much better. I added the ability to directly record a video from the emulator using ffmpeg. Here is a video showing off a few games that work well.
8/23/2020: Added an nsf player. The format is not 100% supported yet as it does not support bank switching or PAL speeds, but most nsf files I can find seem to play properly.
