Tench is right - prior to Opteron, AMD had NO servers with a major vendor - just a few white box offerings. I don't recall offhand what their 'market share' was, but it would have been in the noise level.
The original Athlon, however, did make quite a statement in the consumer space, reinforced by the Socket A products which introduced several advanced concepts (mostly cribbed from Alpha) and held the performance edge from late 1999 until Conroe. Even then, AMD did not penetrate the commercial desktop space to any significant extent.