Fortunately, characterizing the performance of these two CPUs is fairly easy, thanks to a startling amount of consistency in terms of relative performance across a range of benchmarks. The Opteron 180 performs exactly like an Athlon 64 X2 4800+, which is to say, exceptionally well. This thing outruns the Pentium D 950ostensibly its most direct competitor from Intelvirtually across the board. The Opteron 180 also outperforms the more expensive Pentium Extreme Edition 955 in the lion's share of our benchmark suite. For high-end, single-socket workstations, the Opteron 180 is as good as it gets right now. Only the Athlon 64 FX-60 is faster, but that chip is targeted at gaming PCs rather than workstations.
The performance picture for the Opteron 165 is more complex. More often than not, the 165 scores higher in the benchmarks than its closest real competitor, the Pentium D 930, but the Opteron 165 doesn't have nearly the dominance that the Opteron 180 does. Although AMD's K8 architecture delivers quite a bit of performance per clock, the Opteron 165's 1.8GHz clock speed is low enough to keep it from really exploiting that architectural advantage. The 165's relatively low memory bandwidth and high memory access latencies in our synthetic memory tests compared to the other K8 chips we tested are testaments to that fact. I would recommend stepping up to a higher clock speed if possible. At 2GHz, the Athlon 64 X2 3800+ looks like a better option for those building their own systems, at least if we're talking about running at stock speeds.
Of course, another way of stepping up the frequency is to overclock the stuffing out of your CPU, and for that wonderfully questionable pursuit, the Opteron 165 is about as good as it gets. [Insert old-timer reference to Celeron 300A here.] There's no guarantee that the one you buy will reach 2.65GHz and run stable like ours did, but you can probably bet that it will reach well beyond its stock 1.8GHz and that its performance at that higher clock speed will be very nice indeed. For a relatively affordable dual-core PC enthusiast's processor, the Opteron 165 looks very attractive. The only thing is, you will need a heavily overclockable motherboard in order to reach the near-300MHz HyperTransport speeds we used to realize this chip's full potential. Some folks may wish to investigate the Opteron 170 as a possible alternative, especially given AMD's apparent efforts to slow supply of the 165. The 170's 10X multiplier will be easier on mediocre mobos, and may be worth the extra cash.