Call of Duty: Warzone at 120Hz - has PS5 back-compat evolved?

The recently released 120Hz update for Call of Duty: Warzone for PlayStation 5 users is a welcome boost - it doubles performance over the prior version of the game, doing so with no noticeable impact to image quality. More importantly, its release may well signify that Sony is beefing up its backwards compatible support for its latest console, bringing it closer into line with the kind of features available on Xbox Series consoles, when running code designed for last-gen machines.

So, in this piece, I'll be considering backwards compatibility features in general for both Microsoft and Sony machines, while at the same time looking at Warzone specifically. But to begin with, there are a couple of caveats and clarifications required for the game's 120Hz support on PlayStation 5. First of all, Activision's patch notes suggest that an HDMI 2.1 screen is required to achieve 120Hz gaming - but this is not the case. If you have an HDMI 2.0 display (or indeed capture card), you can still achieve 120fps - however, the image will be internally downscaled from native resolution to 1080p.

There have also been reports that the PS5 needs its game presets option in the game/app settings menu set to 'performance' but this can be ruled out. To activate 120Hz, all you need to do is ensure that in the Screen and Video menu, the 'enable 120Hz output' is set to 'automatic'. However, we can confirm that there is an issue with Warzone HDR - if you have high dynamic range enabled, or set to automatic, 120Hz will not work. This front-end option needs to be disabled, which is a shame. I tested this on both an HDMI 2.1-equipped LG CX OLED and on an HDMI 2.0 capture card.

With the game confirmed working at 120Hz on PlayStation 5, we compared Warzone with the Series X version using the spectate function. Essentially, we boot the game on both consoles, then buddy up and join the fray as a duo. From there, the aim is to die as quickly as possible and then lose in the gulag. After that, both PS5 and Series X spectate the same player, giving like-for-like gameplay feeds. We captured both at 1080p120 (though Series X can output 1440p120 for capture devices) and also took full 4K system level screenshots, which you'll find lower down the page.

How they compare brings us onto a different topic - how back-compat works on each console. Microsoft has been open about this. With the its SDK, games can query the hardware to find out exactly what system it is running on. From there, added modes and features can be enabled - like higher resolutions, 120Hz support or even different graphics settings, as seen in Cyberpunk 2077, for example. Sony has not been forthcoming on how this all works on PS5, but having now seen developer documentation, it does now seem that it works in the same way. There's an 'sceKernelisProspero' system call developers can use that returns 1 if running on PS5, 0 if it is not (Prospero is Sony's codename for PS5).

So, if that is the case, why have we typically seen less ambitious back-compat support on PS5 compared to Series X? It's not 100 per cent clear, but the most likely explanation is that PS5 adds CPU and GPU horsepower from the new hardware and also benefits from faster storage. However, system level limitations from PlayStation 4 Pro remain in effect - and fundamentally, this suggests that even with back-compat offering so much more over PS4 Pro, there's likely no scope for overcoming the Pro's relatively limited 5.5GB of useable memory. Meanwhile, on the Xbox side, Series X will be able to address at least the same minimum 9GB pool of RAM as Xbox One X. Things may be changing on the Sony side, however. 120Hz output is not supported at the system level on PS4 - but clearly it is happening with Warzone on PS5, which we can confirm is still very much a PS4 app.

But as much as back-compat features matter, so does the nature of the original code. Yes, there are differences on Warzone running on Series X and PS5. The most noticeable is the ring of green gas that encloses the titular warzone, which is dynamically generated and varies in density on a per-client basis, making it more difficult to see through for some players compared to others. It's not a console-specific thing, it's random for all players. Level of detail is also dynamic - I noticed that pop-in in the mid-distance could favour PS5 or Series X at any given point, though the Microsoft machine did seem to have an advantage here. Even with all four high resolution texture packs enabled (a fifth has been added since our testing), Series X also seemed to exhibit an advantage in ground texture resolution in some areas too.

Again, none of this is directly related to console specifications - it's more than likely down to the legacy limitations of the last-gen consoles, such as available memory. And that is the best explanation for the big resolution differential too - again, 'ported over' from the last-gen machines. PlayStation 5 appears to render Warzone at an internal resolution in a window that's typically 1512p to 1566p. Meanwhile, the Series X looks visibly cleaner - in 120Hz mode, it seems to run at 1920x2160 usually, reconstructing up to 4K. So, while both consoles can output a 4K signal at 120Hz, native resolution is lower: PlayStation 5 is visibly blurrier than Xbox Series X, as the comparison shots on this page demonstrate.

The tables turn when we look at performance where undoubtedly, PS5 has a commanding advantage. Both versions of the game can drop frames - dramatically so in the sequence before the initial drop, but actual gameplay is pretty one-sided. For the vast majority of play, PlayStation 5 is mostly locked to 120 frames per second with full v-sync. So, in common with quite a few 'back-compat plus' titles, you're getting the same resolution as the PS4 Pro game, but it is matched with a 2x performance multiplier. There can be small dips beneath but it works for me as a really good 120Hz experience. Clearly there are issues on Xbox Series X. It's rare that the game locks to 120 frames per second and typically performance lingers in the 90-110fps range. Screen-tearing in the top-third of the screen is also commonplace.

Now, it is important to point out that the difference between 30 and 60fps and 90 to 120fps may well be the same 30fps but the experience is very different. Moving from 30fps to 60fps sees frame-time drop by 16.7ms. However, dropping from 120fps to 90fps sees a frame-time variance of just 2.8ms. The issue for me is not so much performance, but the v-sync judder you get, which is intrusive to the experience to the point where I'd prefer to play at 60Hz instead. The answer here is to engage variable refresh rate - VRR - which puts the console in charging of when to update the display. VRR is currently Xbox-only and is an absolute game-changer in scenarios like this. PS5 is faster with its almost locked 8.3ms update, but with VRR, Xbox's 8.3ms-11.1ms update still looks super-smooth. Warzone veterans may be able to tell the difference, but I can't. You get that huge upgrade over 60fps and you still get a much cleaner image.

In terms of preference, I enjoyed Warzone most on Series X at 120Hz, but only with VRR enabled. If VRR is not an option, PlayStation 5 produces a less pristine but certainly much smoother experience if very high frame-rate is what you're looking for. Beyond gaming at 120fps, the 60fps experience has not changed much since we last looked at the game. There's the same (or very similar) 1512p to 1566p dynamic resolution on PlayStation 5, while Series X does not seem to require its horizontal resolution scaler - all of our test images came back as a native 2160p. The DRS scaler may kick in during the most heavy play - this is the One X code at its heart, after all - but it didn't come up in our test samples.

In summary, Warzone is an interesting example of the relative strengths and weaknesses of backwards compatibility on the new systems, in a number of dimensions. In the past, we've seen PlayStation 5 frequently double the performance of PS4 Pro without compromising resolution, and that's exactly what Warzone delivers. So, in that respect, if you're a PS5 owner with a 120Hz screen, this update delivers an excellent upgrade with only the mysterious lack of HDR support counting as a negative point. But with that said, despite the 120Hz system level support, the unchanged resolution from PS4 Pro just suggest that there are still last-gen legacy limitations that stop Warzone from being everything it can be on PS5 - hence the unchanged resolution, even at 60Hz.

Meanwhile, on the Series X side, we don't see the same doubling of performance, and I would expect that to be down to the fact that on back-compat titles, it is rare to see a 2x performance multiplier - and PS4 Pro ran the game more smoothly than One X to begin with. However, Warzone on Series X inherits the higher resolution of Xbox One X, while LOD and texture improvements - although quite inconsistent - are also welcome. But perhaps crucially, Microsoft deserves kudos working over years to accommodate the key enhancements of the HDMI 2.1 spec - principally, 120Hz and variable refresh rate support. Their deployment on Xbox One and One X were more of a technical curiosity, but with Series consoles and the extra horsepower available, these features have come into their own.

Will we see the same on the Sony side? Based on the most recent SDK roadmaps I've seen, VRR support is still noted as a 'TBD' feature - but hopefully we will see movement on that soon. In the meantime, it's great to see that 120Hz is now available for PS4 apps on PS5, so hopefully more back-compat plus titles can tap into it. But with that said, native PS5 and Series X applications are surely the way forward. Raven Software has already confirmed that this is happening with Warzone, and it's the best way to get the most from the new hardware - be it via utilising the higher-end features of the RDNA2 graphics architecture, or really putting new storage through its paces. And when Warzone is updated, we'll be sure to report back on it.

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