Phenom got soundly beaten by the first few Core i generations (Nehalem, Sandy Bridge) in terms of both peak performance and power efficiency. Bulldozer (The bas

Phenom got soundly beaten by the first few Core i generations (Nehalem, Sandy Bridge) in terms of both peak performance and power efficiency. Bulldozer (The basis for AMD's FX and "A" series CPUs) was mostly a misstep that was doomed to feed the very low end of the market. The only truly successful devices based on it were Xbox One and PS4. (Incidentally, those processors used "Jaguar" cores which evolved from Bulldozer but actually didn't inherit the shared execution units (CMT) that were Bulldozer's headline feature that turned out not to work as well as intended.) So between about 2010 and the introduction of Ryzen in 2017, there really was no alternative to Intel if you were building a PC that was either fast or energy efficient. In terms of performance, the 1000 & 2000 series Ryzens roughly attained parity with Intel, while the 3000 series now pulls ahead in many multithreaded and some singlethreaded disciplines, and definitely has better performance-per-watt under load. Ryzen still draws significantly more power than Intel's CPUs when idle though - the PCIe 4.0 transition has counteracted the improvements from the 7nm shrink in this regard, and the APU variants lagging the GPU-less SKUs by almost a year in terms of process and microarchitecture means you also have to power budget for a discrete GPU, which adds a few idle watts. (The most power efficient at idle Ryzen build I'm aware of is the Asrock DeskMini A300, which uses no chipset, combined with a low end APU - this draws about 7W when idle. In terms of performance and expandability, this system isn't any better than a NUC, which draws somewhat less power when idle. You can't buy a full size A300/X300 motherboard though, for some reason, even though this would actually be quite an interesting setup.)