The Xbox 1's ESRAM

Discussion in 'Console Technology' started by LoStranger, Jun 26, 2013.

  1. eastmen

    Legend Subscriber

    Joined:
    Mar 17, 2008
    Messages:
    10,000
    Likes Received:
    1,503
    would depend on how big the data block is . IF your working on something that doesn't fit in 6mb but fits in 32 then you should see big gains but will most likely loose performance as the block gets bigger than 32megs.
     
  2. DrJay24

    Veteran

    Joined:
    May 16, 2008
    Messages:
    3,893
    Likes Received:
    633
    Location:
    Internet
    The CPU cannot access the eSRAM as far as the leaks say, only the GPU.
     
  3. Betanumerical

    Veteran

    Joined:
    Aug 20, 2007
    Messages:
    1,602
    Likes Received:
    56
    Location:
    In the land of the drop bears
    I don't think you'll gain that much tbh. the 32MB eSRAM only has a 30GB/s link to all 8 jaguar cores and each jaguar module (4 cores) can only read/write at 20GB/s at most.
     
  4. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    The diagram does not indicate that AFAICS. How are you drawing that conclusion?
     
  5. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    What why not? At 60 fps the cpu could deliver 512MB per frame... thats 16 times the size of the ESRAM.
     
  6. Betanumerical

    Veteran

    Joined:
    Aug 20, 2007
    Messages:
    1,602
    Likes Received:
    56
    Location:
    In the land of the drop bears
    Because we are talking in the terms of a cache there, speed wise its pretty slow. You'd get the exact same speed going to the DDR3 you'd just have a higher latency.
     
  7. warb

    Veteran

    Joined:
    Sep 18, 2006
    Messages:
    1,057
    Likes Received:
    1
    Location:
    UK
    It would be an additional cache on top of the main memory. 30GB/s would be plenty.

    Low latency is the point for a cache, but would there not be added latency for the CPU accessing eSRAM here, since it's for/on the GPU?
     
    #67 warb, Jul 6, 2013
    Last edited by a moderator: Jul 6, 2013
  8. DrJay24

    Veteran

    Joined:
    May 16, 2008
    Messages:
    3,893
    Likes Received:
    633
    Location:
    Internet
    [​IMG]
     
  9. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    Again the diagram does not indicate that its not accessible by the cpu anywhere on it. Not in symbology, or in diagram form. What about that diagram indicates what you stated?
     
  10. gurgi

    Regular

    Joined:
    Jul 7, 2003
    Messages:
    605
    Likes Received:
    1
    Perhaps he meant not directly...
     
  11. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    I don't even see that. He seems pretty sure but the proof can't be that document.
     
  12. dobwal

    Legend Veteran

    Joined:
    Oct 26, 2005
    Messages:
    5,163
    Likes Received:
    1,172
    Vgleaks mentioned that esram must be flushed before it can be accessed by the cpu.

    But for gpgpu purposes does that matter? CPUs use caches to avoid calls to main memory. How does moving general tasks over the gpu alleviates the need for that avoidance? Gpgpu isn't just about making a gpu suitable for general purpose code. Its also about using a gpu to accelerate those tasks.

    Accelerating general purpose code would seem to me to warrant cache increases in the gpu.

    Isn't parallelizing traditional gpu tasks easier because the workload tends to be composed of more independent operations than found in general purpose code? Would the general mechanism for hiding latency on a gpu be suitable for all forms of gpgpu code?

    I remember there was a paper called CPU assisted GPGPU, where a contributor was AMD. And it talked about using the caches on the CPU to facilitate the memory needs of gpgpu tasks on an APU.
     
    #72 dobwal, Jul 6, 2013
    Last edited by a moderator: Jul 6, 2013
  13. Esrever

    Regular Newcomer

    Joined:
    Feb 6, 2013
    Messages:
    690
    Likes Received:
    441
    Well the 30 GB/s through the northbridge would be plenty if the GPU memory system doesn't introduce much more latency. Can the cpu directly send data from through the northbridge to the gpu without touching ram?
     
  14. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    Well since the 30gb connection says coherent read and write which is a totally separate and independent path from the Main RAM...i would say yeah.
     
  15. DrJay24

    Veteran

    Joined:
    May 16, 2008
    Messages:
    3,893
    Likes Received:
    633
    Location:
    Internet
    It seems pretty clear to me. The eSRAM is local to the GPU and indirect to the CPU. Every system is connected to the rest through some pathway, but getting from A to B doesn't always mean it is fast or efficient.
     
  16. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    I understand that. There is still nothing about the diagram that supports your original claim. From the writings of various developers it seems the opposite is true.
     
  17. DrJay24

    Veteran

    Joined:
    May 16, 2008
    Messages:
    3,893
    Likes Received:
    633
    Location:
    Internet
    My claim is simply the CPU doesn't utilize the eSRAM, is that news? It is clear to me in that diagram and If you read the VGAleaks Durango memory article they only mention eSRAM with regards to the GPU. So which devs have broke NDA and discussed how the eSRAM is used?
     
  18. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    No one broke NDA. Just descriptions of how the ESRAM could should be used. The descriptions are spread throughout the site in the various Durango/xbox one HW threads. Lots of insight from sebbbi and Gubbi in particular. You could be right but your hypothesis is the first I heard since discussions of the esram have been going on in earnest. No one iirc has ever said that the ESRAM was inaccessible by the CPU.

    Of particular note were several discussions related to internal bandwidth and the overall memory subsystem. Your point of view never came up which is why I'm inquiring.
     
  19. DrJay24

    Veteran

    Joined:
    May 16, 2008
    Messages:
    3,893
    Likes Received:
    633
    Location:
    Internet
    I've read those discussions, they were some time ago before any details leaked. If anyone else wants to add their insight, I'd be happy to read it. I thought after the VGA leaks it was just apparent the eSRAM was part of the GPU sub-system, just like in the 360.
     
  20. blakjedi

    Veteran

    Joined:
    Nov 20, 2004
    Messages:
    2,975
    Likes Received:
    79
    Location:
    20001
    There is no dispute that the esram is on the same part of die where the gpu is and behind the graphics memory controller. But my understanding, based on those conversations, particularly the ones where the 30gb/s pathway was discussed in terms of adding to the 200gb/s bandwidth claim was that the CPU and gpu could both access the ESRAM and the system RAM. Now with your assertion in questioning my recollection.

    Either way its not clear from the diagram even with the acknowledgement of gpu managed coherency. You could be right. I just don't know.
     
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...