The code name of the DEC 10/100 ethernet chip, the DS2114x. Donald Becker at Cesdis uses these things almost exclusively in their Beowulf clusters.

Update: Intel purchased the DEC semiconductor line, so now Tulip chips are being made by Intel. Lite-On also makes a clone, and PNIC and NetGear relabel them. Also, Donald Becker is no longer working at NASA, and so is hosting all his Linux device drivers at his site.