When the Xbox 360 version of Sonic Unleashed became backwards compatible with the Xbox One last November, I was shocked that the PS3 version of the Teen Wolf-themed installment of the Sonic the Hedgehog series the same treatment for the PS4. The Xbox 360 and PS3 versions of Unleashed had gorgeous Pixar-esque gameplay graphics thanks to the Havok and Hedgehog Engine, so the latter version couldn't be any different from the former. Meanwhile, the Jak and Daxter series became backwards compatible for the PS4, and most other PS2 games won't see the light of day again on the PS Store. Fortunately, Sony might bring those old games out of the woodwork with a backwards compatibility feature for the PS5 that may allow players to play not only PS4 games, but also PS3 and other legacy games as well.
According to GearNuke, the patent filed by Sony Interactive Entertainment and published on the Japanese digital patent library of the National Center for Industrial Property Information and Training (NCIPIT) is titled "Simulation of legacy bus operation for backward compatibility."
As the name suggests, the patent outlines a method of the PS5's emulation of bus operations of a "legacy device" to execute a "legacy application." In other words, it would mimic, for example, a PS2's hardware bus–in technological terms, a communication system between hardware and software components in a computer or other electronic devices–and run a PS2 game like the original console would without receiving a message that says otherwise.
The patent doesn't explicitly mention the PS5, yet Mark Cerny, the lead architect of the PS4, is listed as its author. Cerny is rumored to be developing the PS5. David Simpson, the lead programmer at Naughty Dog, is also listed on the patent. This patent was registered along with the prior "Impersonating CPUID for backward compatibility" patent published on January 31, where Cerny shares credit with Simon Pilgrim, a programmer for Sony Computer Entertainment Europe.
Backwards compatibility for old PlayStation games could work in theory, but not every game in its library will qualify for the feature for various reasons. For example, the original Crash Bandicoot and Spyro the Dragon won't be backwards compatible for the PS5, but Crash Bandicoot: N. Sane Trilogy and Spyro Reignited Trilogy would since all the games within each collection were remastered from the ground up.