Questions about PS2
- Thread starter Liandry
- Start date
That's what I was asking, but while there isn't an ironclad official answer I can point to I'm pretty certain it has to be 300MHz (or 294MHz or whatever the original EE clock speed was)
I found interesting info about texture decompression on PS2. It's here on page 16
https://www.dropbox.com/s/588z1a7qtpoy0bm/EE_Overview_Manual.pdf
Also a picture.
I was thinking about how useful that may be. So I made two schemes. Maybe someone can comment on them.
Let's say there is 4 textures 32 KB each when compressed, and decompressed texture is 128 KB. That will require 128 KB for 4 textures, and temporary 128 KB for uncompressed texture. Tht is total 256 KB.
Second scheme. There is two textures in RAM, each is decompressed already and require 128 KB. And there is two sets of two textures each. That is 512 KB. Twice more than on scheme 1.
First option saves RAM, secon saves bandwith. What do you guys think about it? Any comments? Maybe there were some mixed options, where some textures are decompressed, and some not, to make some balance between RAM savings and bandwith savings?
https://www.dropbox.com/s/588z1a7qtpoy0bm/EE_Overview_Manual.pdf
Also a picture.
I was thinking about how useful that may be. So I made two schemes. Maybe someone can comment on them.
Let's say there is 4 textures 32 KB each when compressed, and decompressed texture is 128 KB. That will require 128 KB for 4 textures, and temporary 128 KB for uncompressed texture. Tht is total 256 KB.
Second scheme. There is two textures in RAM, each is decompressed already and require 128 KB. And there is two sets of two textures each. That is 512 KB. Twice more than on scheme 1.
First option saves RAM, secon saves bandwith. What do you guys think about it? Any comments? Maybe there were some mixed options, where some textures are decompressed, and some not, to make some balance between RAM savings and bandwith savings?
Are you 100% sure about that?
Well, I was told that if I read the documentation closely I would see that.
Yes, for that number to be accurate the VUs must be run at EE core speed. The Sony article I linked earlier says it outright (in case anyone missed it: https://www.dropbox.com/s/5ypfnlupv0grolo/Vector Unit Architecture for Emotion Synthesis.pdf):
This doesn't include the EE's FPU, it's just VU0 + VU1. It's explained via:
VU0: 4x FMAC + 1x FDIV = (8 + 1/7) * 300 = 2442.86 MFLOP/s
VU1: 4x FMAC + 1x FDIV + 1x FMAC (EFU) + 1x FDIV (EFU) = (8 + 2 + 1/7 + 1/7) * 300 = 3085.71 MFLOP/s
EEcore: 1x FMAC + 1x FDIV = (2 + 1/7) * 300 = 642.85 MFLOP/s
Total: 6171.42 MFLOP/s
The true number is also a little lower with launch PS2s because the EE was clocked at 294MHz instead of 300MHz, so more like 6048 MFLOP/s.
This article was released in the March-April 2000 edition of IEEE Micro, so basically around the same time PS2 launched. It includes a die shot of the EE and everything. So it's very unlikely that it was made in advance of a dramatic redesign that ran the VUs at half speed. It doesn't make sense to run SIMD at lower clock speeds anyway unless you're doing it to implement wider vectors over time and hide latency. But since you can see the four FMACs in the die shot they're clearly not doing this, and since the EE also does an FMAC at 4 clock latency at full clock speed there's no reason why the VUs wouldn't be able to.
I can't find anywhere in the documentation that gives the slightest hint that VUs are run at bus speed and being told to go search through them to find the justification is pretty dissatisfying. Maybe the VIFs run at bus speed (would make sense) and the confusion arises from there.
You are right! I also ooked at all papers and can't find anything. Also interesting idea what VIFs can run at half speed. Maybe Corysama can say something about it.
Was able to find a statement by Fafalada here on B3D from 2006:
https://forum.beyond3d.com/threads/beating-emotion-engine.29352/
Apparently there was some stuff on Wikipedia about half speed execution that sounds like nonsense.
Fafalada said:
https://forum.beyond3d.com/threads/beating-emotion-engine.29352/
Apparently there was some stuff on Wikipedia about half speed execution that sounds like nonsense.
Good find, I'm really surprised that pcsx2 developers were wrong about this (including cottonvibes..).
Every game uses SPU2 in some capacity because that's the only way to output audio.
As for why developers may also use the EE to process audio data, it's because SPU2 is a fixed function mixer that only supports a limited number of processing features. For instance, if you want to perform any 3D positional audio effects SPU2 can't help you. Likewise if you want to decompress streamed MP3 audio SPU2 can't help you.
So, sound processing take part of EE power.
Can anyone tell what exacty VIF0 and VIF1 doing? Did EE reay needed them? And is there something similar in PC CPU?
I don't follow your explanation, but yes the IPU was never (AFAIK) used for what it would have been really useful for.
Theoretically even with 32 bit textures, with optimally clipped and mapped textures you'd never need more than maybe double or triple of what the frame buffer takes up (because of overdraw and blending).
That means that it would actually save a lot of main memory by using 16bit - 32 bit textures (to the extent that 32 bit textures could even be useful) If you use the IPU for JPEG decompression. You'd still have the same 10 - 20 Mb per frame to send textures to eDRAM, which as mentioned, with a bit of culling and MIP map selection scheme set in place should be more than enough.
If you, for some reason insisted on using CLUT textures maybe you could still use the IPU with very low compression, so low that it would in effect be lossless and not affect the CLUT 8 or 4 bit references.
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I finished WRC, WRC II Extreme and WRC 3. Now playing WRC 4. I've noticed big diffeence in graphics. Especially between WRC II Extreme and WRC 3, and between WRC 3 and WRC 4. This is unbelivable achievements. WRC 4 easily can compete with Colin McRae Dirt on Xbox 360. And in terms of dust effects and other particle effects it's even better. Also in WRC 4 thee is amazing amout of trees on screen. This is also looks like it is beyond Dirt. Also maybe anyone can tell were WRC games on PS2 30 fps or 60 fps?
