Editing Project Nested

|version = 1.3

|active = Yes

|platform = [[Super Nintendo emulators|Super Famicom (SNES)]]

|source = [https://github.com/Myself086/Project-Nested Git]

'''Project Nested''' is an open-source [[Nintendo Entertainment System emulators|Famicom (NES)]] emulator for the [[Super Nintendo emulators|Super Famicom (SNES)]] written in 65C816 assembly and C#.

|'''[https://github.com/Myself086/Project-Nested/releases Official releases]'''<br/><small>GitHub releases</small>

The project began in 2015 as a NES emulator on PC. The emulator was running at full speed, and development was going "pretty well", but was not considered challenging, so it was decided to move it to the SNES. After three years of casual development and thinking about how to achieve 100% performance (otherwise it would have been considered pointless) until summer 2018, the emulator began official development.

The current model has been improved since, but not by much. The speed was calculated by multiplying the average amount of times each instruction executed each frame and the overhead. However, the maths were 5 percent off on first implementation. Most implementations were made after approximately one month.

The emulator was inspired by the SNES originally being designed to be backwards-compatible with the NES and Myself086 wanting to code a JIT (Just-In-Time) compiler.

Emulation works by converting NES ROMs into SNES ROMs using a JIT (Just-In-Time) and AOT (Ahead-of-Time) compiler (with various options) for Windows, allowing them to run on SNES hardware.

Save files are created after the software title runs for a while. These can then be added to the ROM, often improving performance, vastly with some titles, and not much with others.

* 16KB of SRAM (support for anywhere up to 256KB of SRAM, depending on the software title and settings, planned)

* A battery if required by the software title

Emulation occurs at up to 60FPS (frames per second) with audio support, but occasional minor slowdown may occur. Software titles that use mappers 0-2 and 4 are playable, with mappers 1 and 4 having minor glitches, which may reduce compatibility levels with titles that use them, mappers 3, 5-8, 11, 12, 16, 18, 21-26, 32-34, 36-38, 40, 42 and 66 unplayable and mappers 9 and 10 unlikely to be supported due to it being declared impossible to accurately emulate CHR bank switching, performed by both mappers. Additionally, iNES 2.0 is not supported.

Out of the 456 tested titles, 31 (6.80%) are fully playable, 93 (20.39%) are playable but need a full playthrough to test, 29 (8.73%) are mostly playable, 157 (34.43%) crash in the intro or early in-game, 128 (28.07%) are unplayable and 1 (0.22%) is unlikely to be supported. For example:

* Punch-Out!!! is unlikely to be supported due to using mapper 9/MMC2, as it hard to emulate because memory banks can be changed mid-scanline when it draws characters FE or FD, or sprites, the hardest to implement. This is not as problematic with the background, as the window can be used to draw and switch the characters.

* One fully playable title, Battle City, was mostly playable from v1.1 until v1.3, when it hung after the game over screen with visual glitches.

Others run with minor glitches or require certain options, such as NMI at vblank or stack native return, to be disabled. Overall, at least 50% of games are expected to run in the future. The official compatibility list is available [https://docs.google.com/spreadsheets/d/1xKZIyNz1DSI3ZBdMfaTEaa_9b6IEABx-ZPwOb6XqcLQ/edit#gid=253005073 here].

* Elite is being used as a model to "aggressively" optimize the EXE, specifically in AOT compilation, to make emulation run at the same speed, or faster if possible.