These are the 5 worst CPUs of all time, ranked

Published Jul 28, 2026, 8:30 AM EDT Nick Lewis is an editor at How-To Geek. He has been using computers for 20 years --- tinkering with everything from the UI to the Windows registry to device firmware. Before How-To Geek, he used Python and C++ as a freelance programmer. In college, Nick made extensive use of Fortran while pursuing a physics degree. Nick's love of tinkering with computers extends beyond work. He has been running video game servers from home for more than 10 years using Windows, Ubuntu, or Raspberry Pi OS. He also uses Proxmox to self-host a variety of services, including a Jellyfin Media Server, an Airsonic music server, a handful of game servers, NextCloud, and two Windows virtual machines. He enjoys DIY projects, especially if they involve technology. He regularly repairs and repurposes old computers and hardware for whatever new project is at hand. He has designed crossovers for homemade speakers all the way from the basic design to the PCB. Nick enjoys the outdoors. When he isn't working on a computer or DIY project, he is most likely to be found camping, backpacking, or canoeing. Every era of computing produces at least one CPU that has a spectacular failure. Sometimes, if you're especially unlucky, you'll get multiple. In the last 40 years, there have been numerous CPU blunders, but these 5 are the worst. Intel Itanium (2001) 64-bit hardware that no one could use Credit: Intel Intel's Itanium arrived in 2001—several years behind schedule—promising to replace the traditional x86 setup that the world had been using. There was one major flaw, however: the performance was terrible. Itanium was a totally new CPU architecture, which meant that you couldn't just run existing x86 applications on it. You needed an emulation layer. That resulted in very poor performance for existing software compared to competing x86 CISC architectures available at the same time. AMD would solve the 64-bit problem two years later without breaking compatibility with existing software. As a result, their approach was widely adopted, which is why you still see AMD64 in use today. If you used Apple products while they switched their lineup from Intel's x86-64 CPUs to their in-house M-series SoCs (which are Arm-based) in 2020, you experienced something very similar. Many applications popular on Macs weren't available for Arm, so Apple implemented an emulator that allowed you to use programs designed for x86-64 CPUs on their new Macs. Intel Pentium 4 "Prescott" (2004) Intel overpromised and under delivered Intel rebuilt the Pentium 4 internally aiming to reach clock speeds of 4.0GHz, but they hit a wall at 3.8 GHz. The result was a CPU that ran brutally hot and sacrificed efficiency for raw clock speed. As a result, people who upgraded sometimes found their new PCs were actually slower than the ones they replaced. The failure was so incredible that Intel canceled the entire follow-up generation shortly after launch. It did lead to the Core 2 Duo, however, so at least something good came out of it. Thermalright Peerless Assassin 120 SE ARGB $34 $37 Save $3 The Thermalright Peerless Assassin 120 SE ARGB is an affordable yet high-performance CPU cooler that can easily keep temperatures in check for any consumer-grade processor. It features six heatpipes and a split heatsink design, paired with two 120mm ARGB fans that give it a premium aesthetic. Intel Pentium with the FDIV bug (1994) Sometimes math is hard, even for computers Credit: Intel In 1994, Thomas Nicely, a math professor doing prime number research, discovered a flaw in the Pentium's math hardware. It would return incorrect answers for some division problems. Intel claimed that the bug was rare enough that it shouldn't affect most people. However, anyone doing serious computational work, like scientists, engineers, or mathematicians, would run into a problem. Eventually, there was a full recall that cost Intel nearly half a billion—a significant sum in 1994. Intel Core i9-13900K and i9-14900K (2022-2023) The most expensive gaming chips destroyed themselves In 2022 and 2023, several flagship CPUs from Intel started experiencing serious problems after only a few months of normal use. Games would refuse to launch or crash, your operating system would experience random crashes, and the instability only seemed to get worse with time. This was no ordinary glitch; the processors were physically degrading, and eventually they'd fail completely. There were a few months of back and forth between Intel and motherboard manufacturers before it was finally revealed to be a microcode problem with the chips themselves that was causing the problem. It took four firmware patches just to prevent healthy chips from degrading, though there was nothing that could be done for the CPUs that were already damaged. Eventually, Intel extended the warranty for 24 different models, which really drives home the scope and scale of the issue. What should you do if you own one? If you own an affected CPU, you should update your motherboard's BIOS immediately and switch to Intel's default power settings instead of any more aggressive presets available. If you bought your chip at launch, you are still covered under the extended warranty. If you were turned down for a replacement earlier, you can now reopen that claim. AMD FX-8150 (2011) AMD's first eight-core chips were a disaster The FX-8150 was marketed as the first eight-core desktop processor. In reality, those cores shared so much hardware in pairs (the front end, FPU, and L2) that it badly hurt performance. As a result, it lost in several real-world benchmarks (including gaming) to AMD's own year-old Phenom II X6 and to cheaper Intel Core i5 chips. The real insult was that the older Phenom II X6 1055T and 1090T were actually great CPUs, which meant that it was better to buy year-old hardware than the "latest and greatest." I quickly returned to my Phenom II X6 rather than continue using the FX processor I'd purchased, and I didn't buy another AMD processor until after the 1600X had been put through its paces by a large enough number of people to spot any glaring problems. CPU failures are inevitable Some would argue the FDIV bug was the biggest CPU disaster because of its fame, but that was one specific flaw in an otherwise decent chip. The FX-8150, by contrast, was bad at nearly everything it did. And multiple CPUs that almost literally cook themselves? That is pretty incredible, even in a long lineup of CPU failures. Even so, CPU disasters tend to be weirdly productive, as if an especially egregious failure is enough to motivate a major improvement. Bulldozer (the FX-series processors) was such a disaster that AMD went back to the drawing board and created Ryzen, which is a great lineup that contains several of the best value CPUs that have ever been made. Prescott's silicon-melting temperatures gave way to the Core 2 Duo. It is a bit early to see what kind of response Intel might have to their microcode debacle, but if history is any indication, it'll be pretty good.