PS2 backwards compatibility remains something of a contentious issue for PlayStation 3 users. US and Japanese launch models featured the principle PS2 hardware built into the system, making for excellent support for almost all legacy PlayStation titles and the ability to run older games with a precision HDMI output. By the time the EU launch rolled up months later, the design was altered, removing the PS2 CPU - dubbed the Emotion Engine - and replacing it with software emulation to mixed results. With Sony still haemorrhaging cash on PS3 production, all PS2 components were removed by October 2007, and backwards compatibility was no more.But the story doesn't end there. Behind the scenes, Sony has been working on restoring PS2 support for all PlayStation 3 consoles regardless of configuration, and we've now reached the point where you can visit the PlayStation Store and download 74 "PS2 Classics" - in truth a roster of immensely variable quality, with only a smattering of stand-out titles. Warnings are given out that the games are running under emulation and may vary from the original PS2 experience, but the real kicker is that you'll have to pay for them - even if you own the original discs. While lesser known games cost between £0.99 to £3.99, most of the titles cost £7.99 a pop.Value issues aside, we wanted to find out more. From a technical perspective, the notion of original PS2 code being able to run under emulation on the PlayStation 3 is a seriously impressive feat of engineering. Ken Kutaragi's finest hour hails from an era where games machines featured custom components built from the ground up, a necessity in an era where PC parts were too expensive to be crammed into a console box. The Sony R&D team responsible for the PS2 software emulator have achieved something of a miracle here - the design of the older console is completely alien to the hardware set-up of the PlayStation 3. The PS2's graphics synthesizer GPU in particular, with its attached eDRAM, offers levels of bandwidth that even the RSX may have issues duplicating."Having phased out support for PS2 backwards compatibility, Sony has been working behind the scenes on a full software solution for all PS3 owners - and the results are impressive overall."
Virtua Fighter 4 Evolution running on three different PS2 emulation schemes - full hardware back-compatibility via a PS3 debugging station (equivalent to an NTSC launch unit), an EU PS3 with partial hardware support and finally the software emulator that runs on any PS3. On this game, the EU machine appears to have a slight blur, while the full hardware model has some poor deinterlacing (only really noticeable in motion). The emulator deinterlaces nicely, generally speaking, giving a 480p-style presentation.
Out of a library of thousands of games, the fact that only 74 are currently available suggests that the emulator remains a work in progress, that many games simply don't work at the moment: not surprising bearing in mind how many developers pushed the system's architecture in ways its creators never even conceived of. Additionally, it is perhaps telling that the big Sony exclusives have no representation - even games that are certain never to get an HD remaster are conspicuous by their absence."We set out to test PS2 emulation on a number of platforms - full hardware backwards compatibility, partial PS2 support from the EU launch PS3 and finally, the new software emulator."
Regardless, we delved into our PS2 game collection, dug out some titles available on the PlayStation Store and ran them on three different PlayStation 3s - our launch debugging station (which runs any PS2 game from any region under full hardware back-compat), an EU launch unit with the hardware graphics synthesizer and emulated Emotion Engine, and finally, a newer PS3 with no hardware support for the older console at all. The latter turned out not to be required at all, so it was quickly disposed of: even if you're running a launch NTSC unit with all the original PS2 hardware contained therein, the PSN downloads still run completely under software emulation.First up, the game that gave us the most curious results of all: Virtua Fighter 4 Evolution. This is a title that relies completely on its 60Hz update - the fundamental interface between game and player is based on that locked frame-rate. As you might expect, there were no problems at all for our debugging station: aside from a couple of tiny, almost imperceptible glitches on a handful of the stage intros, there were no issues with frame-rate at all. The emulation works out OK for the most part, though the glitching does seem to intrude occasionally into gameplay. However, on Jeffry's stage, the effect is far more pronounced, with the game often slipping into what feels like slow motion with dropped frames and borked deinterlacing, resulting in screen-wobble. In these areas, the quality of the gameplay is fundamentally compromised.Switching the game onto our EU launch PS3 with Emotion Engine emulation, we find a curious middle-ground between the two extremes: gameplay is mostly similar to the "full fat" PS3 experience, but there are stages where the game suffers the same frame-dropping/deinterlacing issue. It's not as noticeable as it is on the emulator, but it's still a bit of a pain nonetheless.These video illustrates the glitching issue rather well. Using the replays stored on the DVD, we can run the exact same gameplay video back multiple times on each PS3 in our collection. Two fights are featured in the video: you'll note that we've synchronised the feeds. In the first fight, set on the troublesome Jeffry stage, you can see the interlacing issue, but more importantly you can see how it actually slows down the gameplay to the point where the exact same sequence of action takes longer to complete."Virtua Fighter 4 has some bizarre frame-rate and deinterlacing issues running under emulation, the same problem appearing on the EU launch PS3 - albeit to a significantly lesser degree."
VF4 Evolution running at full resolution on three different PlayStation 3s. Note how the emulated version has issues deinterlacing in the first fight, dropping frames and running slower than the other two. In the second fight, the game runs fine on all consoles. Use the full-screen button for full resolution.
It's worth pointing out that of the various games we tested, this was pretty much the only instance we could find of the emulation not coming up to scratch. Elsewhere, it seems that Sony has done a hell of a good job in using software alone to recreate the full power of the PlayStation 2.It's certainly been a bit of a long haul in returning PS2 support to Sony's current-gen console. Within months of the initila NTSC launches, Sony already had fairly decent software emulation of the Emotion Engine CPU complete - enough for the firm to feel confident in removing the chip completely from the debut EU machine. Yet PSN downloads of PS2 titles only began in earnest earlier this year. An educated guess would be that the unique technological make-up of the Graphics Synthesizer GPU caused issues for Sony's engineers.Similar to the Xbox 360's GPU set-up, the PS2 has embedded memory (eDRAM) attached to the GPU - 4MB of it, specifically. At the time the machine launched, this offered developers hitherto unheard of amounts of bandwidth - 48GB per second according to Sony's spec-sheet. Ultra-quick by nature, and faster than anything available in a consumer level PC of the time, replicating the GS chip within the PlayStation 3 must have been something of a challenge.The software emulator seems to have some issues in certain situations, causing frame-rate drops that physically slow the game down in exactly the same way we saw in Virtua Fighter 4, but they are few and far between and do not cause any substantial issues in the games we tested - Capcom's God Hand being a case in point. Something of a fan-favourite, Clover's insane fighting game illustrates this point rather nicely. You'll note that while gameplay seems to be a match on emulation (note the special moves at the end of the video - there's an identical performance dip), the cut-scenes de-sync as the emulator struggles with the alpha-intensive shot right at the beginning of this video.
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