Hexus.net have got themselves a review of the AMD Athlon XP1900 CPU. Snip:
"Most of the questions surrounding the XP1900 will settle on it's performance since we've covered the new Quantispeed stuff during the arrival of the original range. We know what makes it tick, but does it tick fast enough to warrant buying one over an XP1800? It helps to consider price here. In the UK at the time of writing, the new processor was a whopping ~£251 while it's predecessor retails for ~£191. Does the speed boost warrant spending £60 for 66Mhz? That roughly speaking £1 per extra Mhz. Not very good since for that to weigh out for the whole CPU, an XP1900 would cost near £2000."