ZSNES is an SNES emulator written in x86 assembly. It was originally made in 1997, and has not been updated since 2007. It is currently one of the most popular SNES emulators.
The ZSNES developers focused on speed over accuracy, so a hefty amount of games have bugs (and some just plain crash). The current 1.51 created more problems than it fixed and many problems still remain:
- Compatibility is lower than any modern emulator due to low accuracy to real SNES system.
- Games crashing - Der Langrisser (freezes after 2-3 hours), Super Mario RPG (freezes in many different points of the game), Star Ocean and many other games have freezing and crashing issues.
- Bad sound emulation - A ton of games sound terrible on ZSNES; Earthworm Jim 2 has missing sound effects, some sound effects are missing or sound like short beeping noises, which is not correct behavior.
- Many of the co-processors, which are actually on the cartridges, are emulated in extremely strange ways. For example, Super FX for example is not clocked correctly - Star Fox runs twice as fast as it should.
- Transparency - Kirby's Dream Land 3, Mecarobot Golf, Jurassic Park and any game that uses pseudo hi-res translucency won't display correctly in the default graphics engine. To get them to display properly in 1.51, you have to press 8 to switch to the old graphics engine, or just use an older version.
- Netplay was removed in 1.50.
Many ROM hacks and ROM hacking tools were made using ZSNES as a testing platform because of its popularity. However, because of the inaccuracies of the emulator, these tools and hacks are broken on other, more accurate emulators and real hardware.
In 2011, byuu released bZSNES - a modification of his bsnes that includes the optional inaccuracies of ZSNES and a similar GUI. This was done as an April Fools day joke. It however only has moderate compatibility with ROM hacks made specifically for ZSNES.