Would 64bit benefit PCSX2 like it did with Dolphin?

[Blyss Sarania]

Ahh. I knew it was generally 32 bit, but the info does say it has 64 bit integer units and some 128bit regs which is why I asked. Seems that wasn't really used much(the 64bit integer stuff at least)

[refraction]

Some ops come as 64bit, but that's about it really

[Dr_Hycodan]

Couldn't we say the same about the GC/Wii? The CPU is basically 32 bit PPC based. How come moving to 64 bit helped that out so much?

[refraction]

Couldn't we say the same about the GC/Wii? The CPU is basically 32 bit PPC based. How come moving to 64 bit helped that out so much?

If you read the rest of this thread, instead of just jumping in, you'll find, it didn't specifically posts #7 and #8

[Carsomyr]

Same for me. Hopefully one of the lingering dolphin devs can shed some light on this, or provide a link

But yes I think the decision was to move to 64bit so the focus was made there, of course 32bit code will probably be different, but as they were dropping it there would be no point.

Aside from the memory restriction being lifted, 64bit doesn't serve much of a benefit for the amount of work involved to port the program to it. But any games on the PS2 needing more than 2gb of ram to emulate means there's something very wrong. Games like the snowblind ones are amongst these because they keep making hundreds of small textures which of course eats memory, which is why they need more than 2gb. If that was fixed you probably wouldn't need more than 1gb

Gregory said something to this effect in the Snowblind Progress thread, I mean not specifically what he would do but that he could write something to speed them up... Unfortunately it has a low priority, making people like me sad But at least it is playable now

[Akio]

64 bit Dolphin is about 40-50% faster than 32 bit Dolphin (no longer supported). Can we expect the same improvement with pcsx2 moving to 64 bit?

Where did you get those numbers? Have you tested it? I heard that it was about 30% faster and even that a Dolphin developer didn't seem to be convinced. I know that the 64-bit builds are faster, but I haven't seen any benchmark results.

As others said, the 64-bit builds are faster mainly because of the fastmem feature. IIRC, a Dolphin developer said that this feature improves performance by about 15-20%.

[Dr_Hycodan]

I mistyped that, I meant to say 30-40%. Would implementing fastmem on pcsx2 not benefit as much because of the way the PS2's hardware works or is it because not enough information is given about fastmem?

[Blyss Sarania]

Fastmem does not require 64bit (as has been said) and PCSX2 already has a a fast memory implementation (as has been said). None of us knows what Dolphin's "fastmem" is, and whether it's like what we have or something different.

[JMC47]

Doing fastmem on 32bit is definitely possible; just something that would have been fairly hacky (more than 64bit fastmem) and no one felt like implementing it.

It's not all fastmem though; one of the things that people miss is that Dolphin was maintaining a 32-bit and 64-bit JIT at the same time; part of what was bogging down the 64-bit JIT was maintaining the older 32-bit JIT. So yes, while the 64-bit JIT is faster naturally, and has fastmem implemented for it, the main reason why it was slower was maintaining the 32-bit JIT and keeping parity. I mean, if you're really dedicated, most of the advancements would have been possible on the 32-bit JIT.

For real though, 64-bit is better and has some big advantages for GameCube emulation; it's just nowhere near the numbers you'd see. Dolphin's JIT sped up by nearly 100% after the 32-bit JIT was dropped simply by having the freedom to implement things more easily and Fiora showing up.

Correction, over 100% in some games.

[refraction]

I'm curious, how come having a 32-bit JIT in there was slowing it down? were the two not separate entities? was there some condition logic in there for most of it? Seems weird that removing a feature would make the same feature in a different bitness so much faster.

In your professional opinion, do you think we'd see any performance gains moving to 64-bit? I don't personally, but then I haven't coded in 64-bit, but neither have I seen any evidence to say otherwise.