Questions about PS2

Discussion in 'Console Technology' started by Liandry, Apr 7, 2016.

  1. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    So, what is VU0 and VU1 clock speed, 150 Mhz or 300 Mhz?

    Thank you!
     
  2. Exophase

    Veteran

    Joined:
    Mar 25, 2010
    Messages:
    2,406
    Likes Received:
    429
    Location:
    Cleveland, OH
    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)
     
    Liandry likes this.
  3. dogen

    Regular Newcomer

    Joined:
    Oct 27, 2014
    Messages:
    325
    Likes Received:
    252
    I've been meaning to ask my pcsx2 buddies, but keep forgetting..
     
    Liandry likes this.
  4. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    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.
    PS2 3.JPG
    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.
    PS2 1.JPG
    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. PS2 2.JPG
    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?
     
  5. dogen

    Regular Newcomer

    Joined:
    Oct 27, 2014
    Messages:
    325
    Likes Received:
    252
    Ok, apparently the VUs run at the BUSCLK speed, which is 147MHz. I don't have time today to check it myself.
     
    Liandry likes this.
  6. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    Are you 100% sure about that?
     
  7. dogen

    Regular Newcomer

    Joined:
    Oct 27, 2014
    Messages:
    325
    Likes Received:
    252
    Well, I was told that if I read the documentation closely I would see that.
     
  8. Crazyace

    Regular

    Joined:
    Feb 9, 2002
    Messages:
    333
    Likes Received:
    6
    6.2GFlops with FPU+VU0+VU1 makes it easy to work out if it's bus speed or not
     
  9. Exophase

    Veteran

    Joined:
    Mar 25, 2010
    Messages:
    2,406
    Likes Received:
    429
    Location:
    Cleveland, OH
    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.
     
    vipa899, Shifty Geezer and Liandry like this.
  10. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    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.
     
  11. Exophase

    Veteran

    Joined:
    Mar 25, 2010
    Messages:
    2,406
    Likes Received:
    429
    Location:
    Cleveland, OH
    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.
     
  12. dogen

    Regular Newcomer

    Joined:
    Oct 27, 2014
    Messages:
    325
    Likes Received:
    252
    Good find, I'm really surprised that pcsx2 developers were wrong about this (including cottonvibes..).
     
  13. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    Question about audio on PS2. AFAIK some dvelopers EE main core for sound processing instead of SPU2. Is it true and why they did it?
     
  14. Exophase

    Veteran

    Joined:
    Mar 25, 2010
    Messages:
    2,406
    Likes Received:
    429
    Location:
    Cleveland, OH
    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.
     
    Liandry likes this.
  15. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    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?
     
  16. dogen

    Regular Newcomer

    Joined:
    Oct 27, 2014
    Messages:
    325
    Likes Received:
    252
    So, IF stands for interface. They're DMA channels. The EE uses them to move data around the system. VIF0 is for VU0 and 1 is for VU1, and the GIF is for the Graphics Synthesizer.
     
    #496 dogen, Mar 31, 2017
    Last edited: Mar 31, 2017
  17. Squeak

    Veteran

    Joined:
    Jul 13, 2002
    Messages:
    1,262
    Likes Received:
    32
    Location:
    Denmark
    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.
     
    #497 Squeak, Apr 4, 2017
    Last edited: Apr 6, 2017
    Liandry likes this.
  18. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    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?
     
  19. dogen

    Regular Newcomer

    Joined:
    Oct 27, 2014
    Messages:
    325
    Likes Received:
    252

    Looks like 60 fps

     
    Liandry likes this.
  20. Liandry

    Regular Newcomer

    Joined:
    Feb 26, 2011
    Messages:
    319
    Likes Received:
    37
    But maybe it's just enulator runs game in 60 fps? :-D
     
    milk likes this.
Loading...

Share This Page

  • About Us

    Beyond3D has been around for over a decade and prides itself on being the best place on the web for in-depth, technically-driven discussion and analysis of 3D graphics hardware. If you love pixels and transistors, you've come to the right place!

    Beyond3D is proudly published by GPU Tools Ltd.
Loading...