Developer Chokri Hammedi (blue0x1) has released EmuFive, an experimental emulator that runs PS5 games on a jailbroken PS4. The best result so far is God of War: Sons of Sparta, which apparently runs at around 40 FPS and above on a PS4 Pro. The PS5 version of Hollow Knight: Silksong boots too, though that game already has a native PS4 release. Both are 2D games, of course, and the developer notes that plenty of other games are still sluggish. EmuFive doesn't run on top of the PS4's own operating system. It's a small Linux system, installed through PS4 Multiboot and started from a GoldHEN payload.

At its core is KytyPS5, the same PS5 emulator that recently got Marvel's Wolverine to run on PC, and showed good progress in many other PS exclusive titles. Rather than emulating the PS5's processor, KytyPS5 hands the game's x86-64 code straight to the host CPU. That's an issue on the PS4, as its Jaguar cores lack the AVX2, FMA, and BMI2 extensions that Zen 2-targeted PS5 games use all over the place. Hammedi's patch gets around it by translating those instructions into older SSE4.2, AVX, and BMI1 equivalents, mostly at load time. That works, but it piles extra overhead onto a CPU that is already far slower.Games can be loaded from a USB drive, the PS4's internal storage, or a shared folder on a PC, though users have to bring their own game dumps, since none are included. Those who want to try it should stick to the official blue0x1 GitHub repository, since fake KytyPS5 repos were caught spreading malware about two weeks ago. Demanding 3D PS5 exclusives are still probably out of reach on the PS4, but this is an interesting development nonetheless.