actually they don't. and the xp 2800+ IS faster than all semprons except the 3100+ since the 3100+ is socket 754. the sempron 3000+ is socket A and the 2800+ beats it.
in that article the celeron 315, intels lowest celeron offering, with a clock speed of 2.26Ghz BEATS the sempron 2500+, which is supposed to be equivalent to a 2.5Ghz intel cpu. dj chris is right the sempron has half the cache of the athlon xp, so therefore is slower.
AMD is true: the Sempron is faster in the two benchmarks they used (Winstone and SYSmark). But we have just carried out a more comprehensive testing session, which says that the Celeron D is often better than the Sempron in real-life tasks. We found our own performance ratings of the processors by calculating the average of the processors relative speeds in the 27 benchmarks we used. The results are normalized to those of the Intel Celeron 2.8:
incase you didn't notice, AMD and Intel alike are always trying to say that their cpu is better than the other, that is why you never trust benchmarks posted on either company's site. always look at benchmarks done on independent sites like xbit labs, or toms hardware guide, etc.