None (be one!)
Michael Abrash wrote his first commercial game in 1982, Space Strike for the IBM PC. The game was a PC booter. Other games he wrote were Cosmic Crusader (1982) and Big Top (1983) for the same system. After working at Microsoft on graphics and assembly code for Windows NT 3.1, he returned to the game industry in the mid-1990s to work on Quake for id Software. Meantime, Abrash also worked on the popular game Doom. Some of the technology behind Quake is documented in Abrash’s Ramblings in Realtime published on the Dr. Dobb’s Journal. After Quake was released, Abrash returned to Microsoft to work on natural language research, then moved to the Xbox team, until 2001.
In 2002, Abrash went to work for RAD Game Tools, where he co-wrote the Pixomatic software renderer, which emulates the functionality of a DirectX 7-level graphics card and is used as the software renderer in such games as Unreal Tournament 2004. At the end of 2005, Pixomatic was acquired by Intel. When developing Pixomatic, he and Mike Sartain designed a new architecture called Larrabee, which now is part of Intel’s GPGPU project.
In 2011 Abrash joined Valve.