The Raspberry Pi is hardly what you'd call a performance machine. Even so, with each iteration, it has been getting faster and more capable—to the point where you can now use the Raspberry Pi 4 Model 4 as a desktop PC. Well, Claude Schwartz has taken the little machine and has pushed it harder than anyone else has managed so far, pumping the clock up to a cool 3GHz.
🎉 3.0GHz CM4 🎉 But total unpractical because cooled with ice spray pic.twitter.com/LZo0Yua0J8October 13, 2021
Claude Schwartz (via Tom's Hardware) didn't actually overclock the standard RPi 4 but instead overclocked the near-identical Raspberry Pi Compute Module 4, which is sort of a headless version of the Model B, as in it doesn't have any video outs or any of the standard IO ports. This possibly made the overclock that little bit easier.
For reference the RPi 4 normally has a core clock frequency of 1.5GHz, although with some passive cooling you can hit 1.8GHz fairly easily. Mount a decent fan on the RPI board, and 2.3GHz is within reach. 3GHz is definitely a push above what you can normally hit, and indeed that was only possible by cooling it with ice spray—so this isn't an overclock that is particularly practical.
It isn't particularly easy for normal hardware hackers to achieve either, as there are limits in the firmware that stop you from hitting anything above 2.5GHz. Claude bypassed these by setting the PLL directly, which essentially dictates the system clock, along with tweaking the voltages. He also used Thermal Grizzly Conductonaut liquid metal under the heat spreader to improve heat dissipation.
Obviously, this isn't intended to be an overclock that just anyone can do, but it's still absolutely an impressive feat and shows what's possible with the right know-how. And Claude Schwartz absolutely does know what he's doing, as he's also the man behind PiStorm, which uses a Raspberry Pi to boost the performance of an Amiga A500.