Sony announced key technical details of the PS5 today (March 18) during a special livestream, but one announcement in particular stood out: while the PS5 will indeed be backward compatible with PS4 games, its features are not as comprehensive as one might expect.

In announcing the PS5's specs, system architect Mark Cerny said that the company is currently testing the playtime of "the top 100 PS4 titles" in preparation for a holiday season 2020 launch. This is in contrast to the Xbox Series X, which has already promised to work with all Xbox and Xbox 360 titles optimized for backward compatibility, as well as all Xbox One games.

While we don't know what's on Sony's list of top 100 PS4 games, it seems safe to assume that popular titles like "Fortnite," "Minecraft," "Rocket League," "God of War" and "Spider-Man" should be playable from day one. However, questions remain about the compatibility of other titles, including upcoming PS4 late releases such as "The Last of Us 2," "Ghost of Tsushima," and "Cyberpunk 2077."

If you are interested in the details, the PS5 will run in special legacy mode when running PS4 games and in pro-legacy mode when running PS4 Pro optimized titles. This allows the system to mimic the older model without having the actual PS4 hardware in the box.

The potential gap in backwards compatibility is one of several factors that could give the Xbox Series X an advantage when it goes up against the PS5 this fall. There is also a slight difference in SSD size and teraflops; the PS5 has an 825GB SSD and a 10.3 teraflop GPU, while the Xbox Series X has a 1TB SSD and a 12 teraflop GPU.

But of course, the real test will be to see how these two consoles perform in the real world when they are released by the end of 2020.