Performance Analysis: PlayStation 2 emulation on PS4

We’ve already talked about the basics. The new PlayStation 2 emulation technology for PlayStation 4 runs the original game with improvements: the resolution has a 4x increase and we have support for trophies. However, when looking at the first three ‘classic’ Star Wars, a question remained: how much faster do PS2 games run on the emulator compared to the original console?

We have a sample of three mediocre games, not much. Still, there is interesting data – especially since the three run with unlocked frame-rate and have a very variable performance on the original console. With sufficient computing power, all games can run, in theory, at fixed 60fps. PS4 doesn’t get there but most of the time, it’s very close, and the experience changes.

Two of the games – Jedi Starfighter and Bounty Hunter – run with v-sync and both double-buffered. Basically, it means that while one frame is read by the screen, the next one is generated internally – the idea is that at the next screen refresh, the new frame is inserted. In good condition, it provides smooth 60fps. The problem is that these games often exceed rendering time, missing the next refresh of the screen, meaning a sudden but often sustained drop to 30fps or less. The result is an ugly hiccup when the performance alternates between different frame rates and different levels of response in the controls.

Few current games run that way. A 30fps lockout levels the experience, or other techniques like triple-buffering or adaptable v-sync are used to level out performance drops when a new frame exceeds the budget. However, by assessing how much faster the PS2 emulator is, the less than desirable conditions of these games allow Sony’s new PS4 technology to shine. We have 60fps most of the time, although it is interesting to note that heavy graphics effects – such as alpha transparencies – still affect the frame rate. It is a clear improvement but it is not an endless one of improved performance.

Although interesting, the results in Jedi Starfighter and Bounty Hunter do not reveal everything. A hard double-buffered v-sync affects the GPU, limiting performance on the original PS2 console and exaggerating how much faster it is on PS4. That’s why we looked at the third game – Racer Revenge – the most revealing.

For this game, the original programmers at Lucasarts opted for a smoother refresh and more responsive controls. To facilitate this, they used v-sync. If the engine does not produce a new frame to match the refresh of the screen, it will change to a new image as soon as it is ready – while the screen is updating with each new frame. It produces smoother gameplay but has a cost: you will see screen-tearing. In the case of a racing game, opting for adaptive v-sync is the best – but it has a bonus for this test. The code is not trying to synchronize with the refresh of the screen so there are no delays – Racer Revenge runs at full speed. It is the best opportunity to see how much faster the emulation is.

The answer is that it is much faster. Racer Revenge can run the game on PS4 via 60fps emulation while the same scene runs at 33fps on PS2. It’s one of the biggest differences we’ve seen – we usually have a 20fps spread so in many scenes, Racer Revenge runs with a 50% increase in performance. The result also slightly favors the PS2 – interestingly, the emulator seems to ignore the original v-sync scheme, with occasional broken frames. However, it continues to impress.

The question remains as to how representative these games are of the emulator’s performance – especially when thinking about more challenging games, possibly the ones that use more CPU. However, the possibilities are intriguing, even if the improvement in the GPU is not as pronounced in other games as it is in these. Shadow of Colossus operates with double-buffered v-sync, such as Jedi Starfighter and Bounty Hunter – how would it benefit to run on the emulator?

Then we have games with adaptable v-sync on PS2 – games like Gran Turismo 4 and God of War games. If there is a decent amount of additional GPU performance, these games can run at fixed 60fps. Combine that with some improvements in image quality offered by the emulator and it would be lovely to revisit these games – comparisons with PS3 remasters would also be interesting …