Has Sony resumed Ps2 emulation on the Ps3?

November 13, 2012

While browsing the Spanish dorums daxhordes, I noticed a very interesting topic.

Apparently, after officially stopping production of Ps2 system, Sony has started to hire Ps2 developers to work on Ps2 emulation debugging.

Here is the picture from daxhordes:

Sony hiring Ps2 devs for emulation debbuging

And if you don’t believe this, then you can see the source in the official page here.

Now, I’ll just use this as an excuse for one of my lectures, this time, about Ps2 emulation on the Ps3 and the history behind it.

The Ps2 was a very complex system, it was hard to code for and this has also resulted in being harder to emulate. This explains why the Vita can emulate the psp, and why Gamecube/Wii emulation was done faster than Ps2, achieving higher compatibility in less time.

To achieve Ps2 backwards compatibility, Sony didn’t even resort to emulation, they basically grabbed a Ps2 and incorporated it into the Ps3. Both the Emotion Engine (the Ps2′s CPU) and the Graphics Synthesiser (the Ps2′s GPU) were soldered into early Ps3′s mother board. This allowed perfect Ps2 compatibility for the Ps3. The Ps3 models that used this hardware were the Japanese and American 20Gb and 60Gb models.

As time passed on, Sony decided to cut costs, they did so by removing the EE and using the Cell BE (Ps3′s CPU) to emulate it. At first, this caused a decrease in compatibility, due to the crappy EE emulator, but it then became better and games such as MGS3, which previously lagged, now run smoothly. The models that saw this change were the 60Gb Pal and 80Gb American models.

Motherboard of a 60Gb Ps3, notice the EE+GS on the far right.

Wanting to reduce more costs, Sony decided to remove the GS and tried to emulate it using the RSX (the Ps3′s GPU). This was a complete catastrophe, not only didn’t it work well, but it dropped compatibility down to 30%. Now, this (crappy) emulator exists in every Ps3 out there, so in a sense, all ps3s are backwards compatible, but they have that disabled for discs. This is the reason we see Ps2 games on PSN, because these Ps2 games were lucky enough to be on that 30%.

Here is a sum up of Ps3 consoles and their BC status:
Ps2 Hardware: EE GS IOP
20/60Gb US/JP: Hardware Hardware Software
80Gb US, 60Gb PAL: Software Hardware Software
Others: Software Software Software

So, what is needed to have full backwards compatibility?
First, the RSX can only partially emulate the GS, to fully emulate it, the RSX might need help from the Cell BE. The problem is, the Cell BE is already fully used:

Core: task
SPU0: IOP (the ps1 CPU found in the ps2)
SPU1: EEDMA
SPU2: Isolation
SPU3: IPU
SPU4: GSEGFIF
SPU5: PS2-SPU2
SPU6: VU1
SPU7: not used (factory disabled)
PPU0: PS2-Devices
PPU1: Emotion Engine

As you can see, the way this emulator works right now leaves the Cell with no room for anything else (except the SPU5, which is about 50% loaded, and the SPU7, which is not used), so to have the Cell BE assist the RSX in emulating the GS, there has to be a complete re-map of what the SPUs and PPUs do to get more room. Maybe enabling SPU7, but if Sony disabled it for a reason, I’m willing to bet that reason was overheating.

With all this said, it’s up to Sony to decide what they want to do to the Ps2 emulator, will they leave it like that? will they improve it? will they re-write it? only time will tell.

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