Did this get lost in a lonely ps3 linux thread (RSX's GDDR3 accessed by CELL) ?

Discussion in 'Console Technology' started by Panajev2001a, Jun 2, 2007.

  1. Panajev2001a

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    Well, this shows you cannot leave ps2dev's forums alone...

    RSX's GDD3 memory is being accessed and USED by the CPU:

    http://forums.ps2dev.org/viewtopic.php?p=53490#53490


    Edit: Reading the ps2dev thread better, it is old news for those forums and although they have been able to reliably make use of the extra VRAM they still have some problems.

    Reading from RSX's VRAM from CELL (and in to XDR) is much slower than having RSX initiate the data transfer (so it would be RSX reading from GDDR3 and writing into XDR rather than CELL reading from GDDR3 and writing into XDR) and this would explain the low performance they are getting from using the extra RAM as swap.
     
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  2. Shifty Geezer

    Shifty Geezer uber-Troll!
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    As for speeds, quick tests on my mtd device show about 131MB/s reads and 10.9MB/sec writes. Far from spectacular, but still could be useful as a higher priority swap.
    So this is the dog-slow access, at least on writes. It'd take 25 seconds to load data into the GDDR! Once in, it could be useful to extend data that can be worked on, such as keeping some images in GDDR and blending them in a graphics app. Of limited worth though. Very slow and limited to one application at a time. Though as there's no decent PS3-specific apps mentioned so far, using this extra memory or not, that's not much of an issue!
     
  3. Panajev2001a

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    It should be possible to write to GDDR3 much faster than that though (although nowhere near the 15 GB/s range), SCE's own tests indicated pretty much that kind of read performance (in the same range as what people are achieving here), but higher write performance (same case: CELL doing reads and writes to GDDR3).
     
  4. nAo

    nAo Nutella Nutellae
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    Are these tests performed using the PPU or SPUs?
    BTW if you want to move any significant amount of data is better to have RSX taking care data transfer
     
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  5. Panajev2001a

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    We know and this is what pisses me off about ps3 linux compared to ps2 linux :(.

    We can understand some of the GOOD practices, but we cannot implement them while on ps2 linux, using sps2dev, we could (if we knew how to) implement all the real world best ps2 development practices at CPU and GPU level. With ps3 linux you have only the CPU to play with.
    It gives me less incentive to play with the whole ps3 linux thingy hehe:p.
     
    #5 Panajev2001a, Jun 2, 2007
    Last edited by a moderator: Jun 2, 2007
  6. Crazyace

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    All of the fun stuff on the PS3 is found on the cell :) - that's my incentive for using PS3 linux..
     
  7. patsu

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    Hi nAo, does it make a difference whether it's from SPU or PPU ?
     
  8. nAo

    nAo Nutella Nutellae
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    Yes, it can make a lot of difference. PPU also does not have a DMA controller/engine
     
  9. nAo

    nAo Nutella Nutellae
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    I partially disagree, you can have plenty of fun with RSX as well (not with linux it seems..)
     
  10. Shifty Geezer

    Shifty Geezer uber-Troll!
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    I suppose most of us see normal GPU's as uninteresting because we only experience them through drivers. But if you can go down to the metal, there's probably a fair bit to play with.
     
  11. Panajev2001a

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    Bah... if it makes you happy :p.
     
  12. AlBran

    AlBran Ferro-Fibrous
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    What sorts of things :?:
     
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