High-level emulation

UltraHLE was an emulator for the Nintendo 64. It was hailed as a massive step forward in emulation technology on its 1999 release. Emulating the N64 (which was only 2 years old at the time) made it the first of the N64 emulators to run commercial titles at a playable frame rate on the hardware of the time.

Earlier emulators had concentrated on accurately emulating all of the low level operations of the target machine. This worked well enough for older consoles such as the Super NES (although truly hardware-accurate emulation wouldn't appear until bsnes) and Genesis.

Co-authors Epsilon and RealityMan realized that since N64 games were programmed in C, they should concentrate on intercepting (the far fewer) C library calls instead of intercepting machine level operations, and write their own code to implement the libraries. Thus, UltraHLE software is in fact an emulator with some parts implemented as a simulation, and the technique is not used in purist emulation projects such as MAME. However, it paved the way for creating playable emulators which use complex graphic routines that require considerable computation power which could be simulated easily with available PC graphic cards.

The final implementation was written in C and used the Glide API, which has since fallen out of use due to being specific to 3dfx adapters. Due to its popularity, several Glide to DirectX translation utilities were made specifically for UltraHLE for non-3dfx video cards.

This high-level emulation had its drawbacks. At the time of release, UltraHLE was only able to emulate approximately 20 games to a playable standard. The software only emulated and simulated the calls that were required for specific games; it was required to adapt the software for games that used different parts of the N64 hardware. However, on its release, it was miles ahead of competing N64 emulator projects such as Project Unreality.

Also notable for its time, UltraHLE was capable of playing commercial games while the console was still commercially viable. Concerned about potential piracy, Nintendo threatened the authors and the site hosting UltraHLE, EmuUnlim, with legal action. Despite this, UltraHLE had grown beyond either its authors' or Nintendo's control. Subsequently, Epsilon and RealityMan abandoned their pseudonyms and went silent.