Fortunately, calling this chip Athlon XP kills off the horrid "Athlon 4" name. As you might expect, this move also brings AMD's model-number processor rating scheme to the mobile segment. From the press release:
Production shipments of the mobile AMD Athlon XP processors, including models 1400+ and 1500+, began in first quarter of 2002. Notebook PCs based on the mobile AMD Athlon XP processor, models 1600+ and 1700+, are expected to be available later this quarter.The chips will be compatible with AMD's Socket A infrastructure, but interestingly, there will be a micro-PGA version of the Mobile Athlon XP, as well. No word yet on when to expect T-bred processors for the desktop to arrive.