YACC (Yet Another Color Computer) was a 68000 (later 68020) computer developed by Apple's Education Research Group (ERG) which would eventually be part of Apple's Advanced Technology Group (ATG). It was developed by Don North in parallel with Big Mac as a test vehicle for adding color to the Macintosh. The color graphics card for the Macintosh II was prototyped on YACC. As with Big Mac, the YACC could run Unisoft Unix as well as the Mac OS.

Parallel Developments
Mac OS - Apple Big Mac - Apple YACC