Just to cover off the natural question of whether the Thoroughbred is exactly on par with the performance of the Palomino, we've taken the liberty of benchmarking both processors using Athlon XP 1700+ models. The following chart tells the tale pretty clearly, and should leave no doubt that the Thoroughbred is simply a die-shrink of the Palomino.
In considering the performance of the Athlon XP 2200+, keep in mind that it's really just a 66 MHz core speed increase over the previous 2100+ model. Only the most optimistic fan would hope that this processor could take back the performance lead from the Pentium 4-2.53 GHz. Of far more importance is that AMD now has a cooler-running Athlon XP model available and possibly a bit more headroom for faster versions.
The most interesting part of reviewing a new processor core (especially one that is also a die shrink) is finding out exactly how much overclocking headroom it has. In terms of overclocking options, the Athlon XP Thoroughbred is virtually identical to previous models. The infamous L2 bridges are alive and well, and although our review chips came without the laser marks, we chose to go the FSB route to match what a retail buyer would experience. The option still exists to link the bridges, but using a 1 MHz FSB increment also helps us get a better idea on its high-end overclocking potential.
On the surface, the 0.13-micron Thoroughbred would seem to have a lot of overclocking potential, but the actual results were a bit disappointing. If you're thinking of buying the Athlon XP 2200+ for overclocking purposes, then stop right where you are. The highest reliable core speed we could get was 1931 MHz using a 143 MHz FSB and a core voltage of 1.775V. You may be looking at the core voltage and wondering why we didn't use 1.8V or higher, and that would illustrate the main problem we had when overclocking.
All overclocking exercises are a give and take between core speed, voltage and overall heat levels and stability. The Athlon XP Thoroughbred took this to a whole new plane, as even slight voltage increases would ramp up core heat quite noticeably (like you had crossed a line in the sand), while lowering the overall overclock speed. Finding a happy medium is a tedious and extremely long-term process, and even hitting over 1.9 GHz took a whole lot of tweaking. For all testing we used a Vantec copper HSF, a 7000 RPM fan and Arctic Silver 3, and it was still tough going at some points.
A by-product of the newer, smaller core is that there is simply less core real estate to work with, thus less coverage using a heatsink. This isn't really a concern with the Pentium 4, as Intel's S478 heat-spreader is the same size regardless of the actual die. We had some questions regarding this and apparently this is one of the reasons why the thermal requirements remain very similar for the higher-end Athlon XP Thoroughbred models. The lower-speed Athlon XP 1700+ (1.5V) is a nice improvement over the Athlon XP Palomino, but once we hit the Athlon XP 2200+ and its 1.65V requirement, the thermal specs start getting a lot closer to the Palomino.
There are improvements with the Thoroughbred, but don't go in thinking of a super cool-running processor, as you will need a heavy-duty HSF and any further voltage increases for overclocking will drive the heat higher. These results got us concerned about the overall viability of the AMD 0.13-micron core, and exactly how the company expects to move above the 1.8 GHz level for upcoming models. We had the same questions regarding the Duron 1 GHz, and as in that case, we are pretty sure a new Thoroughbred core revision is in the works that'll allow higher speeds.
