I currently run (and now with the AMD Optimiser and Processor Drivers for Vista) a stable AMD Athlon 64 X2 3800+ (2.0GHz 2x640K) AM2
In the past, after Intel Pentium II; my processor purchases were Athlon/Semperon. Simply because they were cheaper for about the same power as the Intel Pentiums.
Athlon = Mid-Range Desktop Processor
64 = 64-bit Core with 32-bit Compatibility Core; Although the earlier models, and Semperons are 32-bit Core with 64-bit Enhancements similar to EMT64 on the Pentium 4 Extreme range.
X2 = Dual Cores (recently the X3 was released, guess the core count)
3800+ = PR3800, or Pentium-Rating. This is basically means this is the equivilant Pentium performance if it was that many MHz. Don't confuse this with it being equal to a Pentium 4 3.8GHz however; as they have SSE2/3 on-chip that allow them far better Floating-Point performance when utilised. Next to a basic Pentium running at that clock speed however, if they were still made; this chip would be equal to that.
AMD over traditional Pentium design, run 7 Instructions per Clock where-as the Pentium only ran 4. This has dramatically changed with the Core 2-Series of chips (Core 2 is the family, Single/Duo/Quad indicate the core count) which now perform far better than their AMD/Pentium equivilants.
An AMD Athlon 64 X2 4200+ is about equal performance overall to a Pentium 4 3.2GHz w/SSE3 & HT enhancements utilised. In turn the Core 2 Duo 1.6GHz is also about the same performance bracket.
Clock speeds mean little nowadays, and it is nice Intel have finally learnt this. Unfortunately for AMD they've learn it too bloody well too.
