Someone on AliExpress is selling a rather unique processor you won't find anywhere else (opens in new tab): a Comet Lake mobile processor with a built-in interposer that allows support for LGA 1151 desktop motherboards. If you want to run an efficient 10th Gen mobile CPU on your desktop, now is your chance!
The processor itself is listed as QTJ2, and is a hyperthreaded Hexa-core chip with a base frequency of 2.4GHz and a boost clock of 4.3GHz. We aren't sure exactly what it is, but it appears to be a production sample that never got produced. The QTJ2 mostly resembles an underclocked Core i7-10750H, for comparison.
The chip is no slouch when it comes to performance, mostly resembling gaming performance to that of a Core i7-8700K from a few years ago. One YouTuber tested the chip out and it had no problems handling a GTX 1080 in Shadow of The Tomb Raider.
Unfortunately, compatibility with this chip is not as straightforward as we would like it to be. Due to the QTJ2's mobile nature, the chip isn't compatible with LGA 1151 motherboards without a BIOS modification. Luckily, the seller of the chip will happily take in your motherboard's BIOS and customize it for you, so the mobile Comet Lake chip can support your board.
There are other limitations worth mentioning. For cooling, you have to ensure the CPU cooler you use has a flat surface. This means coolers with heat pipes that directly contact the CPU are not an option (like the Hyper 212 EVO), because the QTJ2 CPU does not have an IHS. You need a cooler with a perfectly even surface to ensure the die is cooled properly.
Another issue is chipset limitations. For some reason, the Comet Lake chip can only be supported on select 100 series, 200 series, and 300 series boards (for example Z390 is not supported). So be sure your chipset can support the chip before you make your purchase.
Still, it's cool to see a mobile Comet Lake chip working on a desktop computer. Ironically, this is the ONLY way to get a proper Intel 10nm based chip inside a desktop at this current time.
Desktop variants of Comet Lake and upcoming Rocket Lake chips are still running on Intel's older 14nm process. So if you're desperate to get 10nm working on desktops right now, this is your only option. Just beware this configuration is officially unsupported by Intel and is only supported by third parties, so make sure you know what you're getting into.