question about Neon SIMD support(android)

[mrtegra2]

Hi im using a tegra 2 based phone without NEON SIMD i have few question here which i think it will be useful in the future

1.what improvement by using NEON simd? is FPS,audio,video or better fps with audio?

2.will tegra 2 based device without neon will be able to play games full speed with audio in the future?

3.the cortex a5 have 128bit NEON simd vs cortex a9 64bit NEON simd,will the cortex a5 will have better perfomance on audio/bgm?

4.will the dual cortex a9 with 512mb ram enough to run PPSSPP full speed with audio in the future?

5.is there any quad core support? that will be huge impact on FPS right?

[[Unknown]]

Currently we don't make enough use of NEON. But the plan is to use it to improve texture loading, audio, and SIMD operations the PSP's CPU supports itself.

There's still a lot to optimize and improve even ignoring NEON, so I can say I'm sure it'll be faster even on non-NEON devices. But there are going to be some games that use SIMD heavily that will probably need NEON to get reasonable performance - that said, I'm just guessing.

Can't know the performance exactly until we write it. I'd expect the A9 to still do better as a guess.

I think 512 MB will be fine.

The PSP itself is NOT multicore. Videos and audio decoding (neither of which PPSSPP does yet) are done on a separate chip, and the GPU processing is done on a separate chip. We can move all of those off the main core, which definitely will help performance. What we can't do is make the game itself multicore - it will definitely break if we do, since PSP games were not written for multicore, and will get confused and trip.

So, in other words, I don't think PPSSPP will ever be able to utilize 4 cores. Probably at best 2 with some small stuff running on a third.

-[Unknown]

[VIRGIN KLM]

That's more than enough actualy. If 3/2.5 cores are dedicated for PPSSPP then the rest 1/1.5 can be dedicated to Android OS operation which would not affect the performance of either.

[[Unknown]]

Yes, but to clarify, many games I've tested are either dominated by CPU/HLE speed, or dominated by actual GPU speed. Even if we use 2.5 cores as much as we can, it won't change this - if the GPU can't draw that many fps, or if the CPU (which'll still be on a single core) isn't able to keep up, it'll still be limited by that.

So my point is that even if it's on 2/2.5/3 cores, I would not expect double the performance. It's possible, and there are other things that we're doing to improve performance, but multiple cores just isn't a silver bullet.

-[Unknown]

[VIRGIN KLM]

Yeah I know that. My point was that CPU would rarely be the/ be less prone to be the bottlenecking factor.

[mrtegra2]

i see....

btw does PPSSPP prefer high single threaded perfomance than multi threaded perfomance? for example high clocked snapdragon s2 like MSM8255T 1.4ghz than dual core tegra 2 for example

[VIRGIN KLM]

Right now it will prefer anything with the most raw power on a single core (most of the times, exceptions are devices like ARMv6 and a couple other cases).

[xsacha]

(04-13-2013 09:47 AM)mrtegra2 Wrote:  i see....

btw does PPSSPP prefer high single threaded perfomance than multi threaded perfomance? for example high clocked snapdragon s2 like MSM8255T 1.4ghz than dual core tegra 2 for example

Yes, just a single-thread. At least 1GHz is recommended by me so as to keep up with the GPU.
The GPU is the more important factor right now if you want nice FPS.
If you don't mind skipping frames, a nice CPU can get you a high VPS though.

[mrtegra2]

(04-14-2013 11:06 AM)xsacha Wrote:  

(04-13-2013 09:47 AM)mrtegra2 Wrote:  i see....

btw does PPSSPP prefer high single threaded perfomance than multi threaded perfomance? for example high clocked snapdragon s2 like MSM8255T 1.4ghz than dual core tegra 2 for example

Yes, just a single-thread. At least 1GHz is recommended by me so as to keep up with the GPU.
The GPU is the more important factor right now if you want nice FPS.
If you don't mind skipping frames, a nice CPU can get you a high VPS though.

about gpu,what is the most important factor for fps?
is it fill rate perfomance,or texturing perfomance or maybe gpu driver?