DOOM finally received its '4K patch' for Sony's PlayStation 4 Pro and Microsoft's Xbox One X. However, early tests from YouTuber VGTech indicate that 4K resolution is never really achieved on the PlayStation 4 Pro, whose maximum resolution is 1440p with vertical dynamic scaling taking place during the more demanding scenes.
On the other hand, the Xbox One X does reach actual native 4K (3840x2160) resolution but often drops below that. Here's what VGTech had to say about both tests:
The PS4 Pro version uses a dynamic resolution with pixel counts ranging between 2133x1440 and 2560x1440. The most common resolution on PS4 Pro seems to be 2560x1440, but the resolution is often below this figure during demanding scenes. The PS4 Pro does downsample when outputting at 1080p.
The Xbox One X version uses a dynamic resolution with pixel counts ranging between 2688x1512 and 3840x2160. The Xbox One X rarely reaches a resolution of 3840x2160. The resolution on the Xbox One X varies a lot so it is difficult to get an average figure, but a common range during demanding scenes seems to be between 2688x1512 and 3072x2160.
This lines up with the early assessment made by NXGamer, another YouTuber who regularly takes upon himself to compare enhanced PlayStation 4 Pro and Xbox One X updates.
— NXGamer (@N_X_G) March 30, 2018
The average frame rate seems to be 57.8 FPS on PlayStation 4 Pro and 59.16 FPS on Xbox One X. In both cases, PlayStation 4 Pro and Xbox One X ran at a higher frame rate when unpatched, though obviously at 1080p resolution.
As a reminder, 2016's DOOM runs on the id Tech 6 engine (just like Wolfenstein II: The New Colossus).