The CPU mix right now is interesting too.
If they still made them, we would still be selling better than 50% of the total CPU mix in Athlon XP 2500s. The Barton 2500 is superior on the desktop to any Celeron, Socket A Sempron, Pentium 4, or small-cache Athlon (2400, 2700 non-Barton, etc). On the desktop it is indistinguishable from the higher-clocked Barton-core Athlons (XP 3000+ for example) and the A64-based Semprons. Only an Athlon 64 outperforms it for normal everyday use, and even then the difference is small. Simply, it was one of the all-time great CPUs. Alas, you can't buy them anymore.
The nearest substitute is the Barton XP2800 - but since AMD put the 2800 price up by quite a lot, these are a non-starter.
So that leaves us using the lack-lustre Socket A Semprons for the low end. The Socket A Sempron 2800 is a reasonable performer, though slower than the old XP 2500 and not much cheaper than a Socket 754 Sempron 3000, so we rarely use those. In any case, we can't source KT-600 motherboards for them any more and have been reduced to sticking in a Nforce II based thing and hoping to Christ that it doesn't bugger up. It is a Gigabyte though, so maybe they will be OK.
In the end, the only reason to select a Socket A Sempron is because you don't want to shell out for a Socket 754-based one (and also because the current model Celerons are complete crap and not even cheap), so if you are buying on prce you might as well have the cheapest one - i.e., the 2200. We will switch to the 2400 when the 2200s run out. Mainboards for these are easy: in this segment, you are only really looking at all-in-one boards, and the Gigabyte VIA-based boards just plug in and work.
I don't know why anyone buys Pentium 4s. They can seem allright on first impression, but the moment you start a second task up they bog down and race along like a champion 100 metre sprinter up to his waist in a sewage pond — lots of arm-waving, very little progress over the ground. We sell, on average, one every couple of years.
The surviving Athlon XPs are hopelessly overpriced. A Socket 754 Sempron costs less and goes equally well on the desktop, better in games.
Of the Socket 754 Semprons, the 3000 is the one to have, though the 3100 is in the ballpark, price-performance wise. The Sempron 3000 is our best-selling CPU right now. We sell roughly 60% of them on a Gigabyte Nforce III board with stand-alone video, 40% on a Gigabyte VIA-based all-in-one board. Although the Nforce III boards have been completely trouble-free so far, I have bitter memories of the bad drivers and poor reliability of Nforce I and Nforce II chipsets, so I'll look into replacing them with a VIA-based board soon. (Why take chances when you don't have to? Gigabyte have a VIA-based board out now, so I'll probably switch to it.)
In Athlon-64 space, the Socket 939 3000 is probably the one to have. It's barely any dearer than the Socket 754 equivalent, so on the face of things you might as well go with the newer platform.
But the hard, cold commercial reality is that it simply isn't practical to try to stock more than a certain number of products. Your economies of scale go down and (inevitably) your prices have to rise to cover that. By buggerising around with five different chip families on six different types of motherboard (you have stand-alone AGP and UMA versons of each of the three socket types, remember) AMD have made life much more difficult for their OEMs.
In the glory days of the XP 2500, we carried just two different motherboards: an AGP board for the 2500 and the high-end 3000, and an all-in-one board for the entry-level 2000 chip (sometimes used for bigger CPUs too, of course). Or go back to the days when the Athlon Classic was the fastest thing in town: you had one board for Athlons, and the FIC VA-503+ for everything else. (Boards with on-board video were such crap in those days that you usually tried to avoid them.)
So we carry the Socket 754 Athlon 3000 in stock and only get in Socket 939 parts to order — usually the 3500, because if you are that keen on performance, then you will probably want to spend the extra anyway.
Overall, at a rough guess, we sell:
30% Sempron 2200 (Socket A)
5% Sempron 2800 (Socket A)
35% Sempron 3000
25% Athlon 64 3000 (Socket 754)
5% Athlon 64 3000, 3200 or 3500 (Socket 939)
5% other stuff
(Yeah yeah, so that adds up to 105%. I exaggerate a bit sometimes. What else is new?)
It wouldn't surprise me to see the Athlon 64 percentage go up quite a bit more over the next couple of months. They will probably become our #1 quite soon.