Xbox Series X [XBSX] [Release November 10 2020]

Discussion in 'Console Technology' started by Megadrive1988, Dec 13, 2019.

  1. iroboto

    iroboto Daft Funk
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    Perhaps one final thought on the concept of clockspeed and CU count. Perhaps this hypothetical case may make more sense.
    If you design a synthetic benchmark which only leveraged the fixed function portions of the hardware only and skipped the entire unified shader pipeline entirely;
    if XSX ran this benchmark at 100fps, PS5 would run this benchmark at 123fps, or 23% faster as per their clock speed difference.
    There is absolutely nothing XSX can do to mitigate this difference because they have exactly the same FF hardware but PS5 runs 23% faster here.
    Which means, in any benchmark of which XSX and PS5 are pretty much identical, XSX essentially made up that deficit on the back half of the frame where compute and unified shaders do its work despite this part also being 23% slower.
    And so that CU advantage there is putting in work to make up the clock speed differential twice.
    I hope that makes sense.

    Effectively the larger the back half of the portion is, or the further away the XSX can get away from fixed function pipeline, the more it will leverage it's silicon strengths.

    I think typically this isn't the case with other GPU families. Often larger GPUS are also shipped with larger front ends so that you don't run into this scenario of clockspeed vs core count. It's more like you have it all so there is no way the more expensive card will perform worse than a model lower on the family.

    Thinking about it this way, XSX is actually the one that is an outlier as it's front end performance and general compute performance are not well matched. Increasing the clock speed would help narrow that particular gap with respect to PS5, but it wouldn't make up for the fact that it's mismatched with respect to itself.

    I don't know if MS had went this route in favour of hoping the transition to Mesh shaders would happen sooner since CUs are what they use to process geometry, and it's not clear on their intentions on whether they hoped developers intend to skip the 3D pipeline altogether in favour of just using compute shaders for rendering out pixels instead of ROPs. It does come across again, as a cost cutting measure.
     
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  2. snc

    snc
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    and imho if some think xsx advantage shouldn't be close to theoretical 20% compute and 25% bandwidth advantage but rather closer to 44% cu count number advantage is simply wrong but end this theoretical dispute here ;)
     
  3. thicc_gaf

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    It's not really "hoping"; things are moving to favor parallelism and wider designs in the GPU space. MS wanted a design that was future-proofed in this respect, and we have benchmarks on mesh shader routines showing incredible degrees of performance uplift over the traditional 3D pipeline process that operates mainly off fixed-function hardware. So perhaps in some way it's a cost-cutting measure but it's no more of one than, say, Sony settling for pseudo-programmable logic with the primitive shaders in their design...and I'd say Microsoft's choices are easily the more future-proofed of the two even in spite of compromises.

    Not to say in practice we will see games leveraging mesh shaders having a tenfold increase over games on the traditional pipeline path, but it's sensible to assume there will be a notable advantage once devs fully move over to that setup and move their pipelines and tools to build around it. This is hopefully where Sony's alterations (whatever they are) with their primitive shaders is sensible and able to match up with what true mesh shaders provide in the near future.

    What we're probably go to see is a clash in 3D design philosophies, at least for the short term, Sony favoring fixed function (and pseudo-programmable graphics with the prim shaders) and Microsoft favoring programmable mesh shaders. However, the advantage seems to be on Microsoft's side here because it's not just Series systems pushing mesh shaders; AMD GPUs, Nvidia GPUs and Intel GPUs are also pushing in that direction, collectively that is a market for hundreds of millions of devices, more than whatever numbers PS5 can reach. So 3P devs will certainly start to optimize their pipelines for mesh shaders (though not at the expense of fixed-function hardware), and it's honestly just a matter of when that happens, not "if".

    If you want a point of comparison, IMO it's like the quadrilaterals/triangles scenario from the '90s between SEGA and Sony, only this time Sony are on the quadrilaterals side of that scenario and Microsoft are on the triangles side of it. What happened then looks like it will happen again (in terms of the general shift; both companies will be perfectly fine in the long-term in spite of this IMHO and support for the fixed-function 3D pipeline is more ingrained than quads were in the gaming space at their time).
     
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  4. iroboto

    iroboto Daft Funk
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    I don't think anyone here thinks its going to be a 44% advantage due to CUs. At least I haven't read it
     
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  5. snc

    snc
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    thats was my impression about this cu count talk without clock and bandwidth ;)
     
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  6. iroboto

    iroboto Daft Funk
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    I think there was an ask earlier on RT performance on whether clockspeed or more CUs would matter. Each CU contains it's own RT block, so naturally, it would get through the RT portion of the of the pipeline faster.
    However.

    From the other thread though in particular WRT the RE8 comparison, and Oleg's all seeing eye: https://forum.beyond3d.com/posts/2202188/

    So even if you have more RT units, you may still be CPU limited on the workload, meaning the RT units may not necessarily be fully utilized.
    ie. RE8 is probably not an ideal benchmark for RT performance since both are likely CPU limited given they are both some form of checkerboard rendering.
     
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  7. snc

    snc
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    Rt capabilities on amd cards are connected with tmu units and scale also with clocks
     
  8. iroboto

    iroboto Daft Funk
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    yea but a 23% clock difference isn't going to make up 44% less RT units.
    If PS5 and XSX are running the same RT frame times, then the additional RT units aren't being used or they are bottlenecked somewhere down the line. Which isn't impossible, we see this happen with ROPs often (bandwidth bottleneck) but I think as a general statement more RT units should outperform less RT units at the same function. There isn't enough clockspeed to make up the differential, nothing controversial by those stating that above.
     
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  9. snc

    snc
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    when did I write it will ? just pointed out that talking about cu count without clock and not simple use tflops and bandwidth as indicator is misleading
     
  10. Jay

    Jay
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    I personally think it's more simpler than this.
    They wanted a specific performance and this was the most efficient and cost effective way to achieve it.
    They wanted a raw 2 times the 1X performance which is 12TF.

    Its not particularly slow or wide, it's just considered that when compared to PS5.
     
  11. ToTTenTranz

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    Yan Chernikov worked at DICE on the Frostbite engine for 5 years, has been developing his own game engine called Hazel and has a ~10 year-old channel with hundreds of video tutorials on how to develop each stage of a videogame engine.

    "Reaction youtuber" is a weird way to write "guy who knows more about videogame rendering than all the other graphics analysis youtubers/journalists combined".



    PS5 and SeriesX have the same number of Render Output Units, but the first runs their ROPs at >20% higher clocks therefore it has >20% higher pixel fillrate.


    All games are using traditional rasterization still (even Dreams uses the ROPs at some points AFAIK). There are now games using a hybrid raster where they mix real time raytracing with rasterization, but they're still using a rasterizer in the pipeline.
     
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  12. mr magoo

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    So if we look at the rendering pipeline as a whole the only thing we can be sure for now is ps5 and xsx will complete different stages of rendering process at different speed and both have advantages in specific areas. As long as the load may differ between different steps, some applications at specific times may favour one over another. Right?
     
  13. ToTTenTranz

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    From what I've been reading from developer statements, it's exactly this.
     
    #2713 ToTTenTranz, May 3, 2021 at 2:20 PM
    Last edited: May 3, 2021 at 3:17 PM
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  14. see colon

    see colon All Ham & No Potatos
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    One things that's great for us interested in rendering load differences is that many games ship with graphics modes and high refresh options that allow us to see differences that may not have been visible at lower framerates or resolutions. That's not something we got in generations past.
     
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  15. thicc_gaf

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    Pretty much. However, from the data we have on both systems right now we can infer there are areas each have advantages on over the other. PS5's main GPU rendering advantages are pixel fillrate, triangle culling, triangle rasterization and faster L0$ on the CUs. Series X's main GPU rendering advantages are texture/texel fillrate, wider L0$ bandwidth and BVH traversal intersection tests for RT, though some of these rely on GPU saturation percentage.

    Some engines work great saturating wider designs (in context to full RDNA 2 GPUs Series X's GPU isn't really that "wide" and at one point 36 CUs were also considered "wide" under some versions of GCN), some don't. But most engines just tend to "automatically" benefit from faster clocks, up to a limit anyway (thinking about certain game logic that might get thrown out of wack).

    That does have an effect WRT pixel fillrate but the config of the ROP backend between the two systems differs; PS5's is older while Series X's is more recent (adhering to what the RDNA 2 GPUs offer on that front).
     
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  16. ToTTenTranz

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    Being more recent doesn't automatically mean it's more performant.
    IIRC the PS5 has more die area dedicated to ROPs but the SeriesX has ROPs that closely resemble RDNA2 PC GPUs. It could be that the new arrangement simply offers die area savings, or area savings with a small cost in performance.
    As an example, one Kepler SM (192sp) provides higher compute performance than one Maxwell SM (128sp), yet the die area savings made it a worthwhile trade-off.
     
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  17. Tkumpathenurpahl

    Tkumpathenurpahl Oil Monsieur Geezer
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    Thanks.

    Right. This is why I think the XSX will perform increasingly better than the PS5 as the generation goes on: the PS5's higher clocks make it a superior rasterisation machine, the XSX's wider GPU and higher bandwidth make it a superior ray tracing machine. As the generation goes on, we're likely to see more games move from full rasterisation, to hybrid, to a point where ray tracing is a major part of the rendering pipeline.

    I suppose the Metro Exodus update will be quite a good early barometer of this.
     
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  18. invictis

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    However real world tests never show that. Digital foundry did tests with the same tflop GPU, with one clocked narrow and fast and the other wider and slower, and the performance was better on the wider and slower GPU. Also, a website did tests on RDNA 1 cards if I recall correctly, where they over clocked the GPU by 18% or something and the game only improved performance by 10% or something similar, in other words the performance didn't scale with clock increases.
     
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  19. iceberg187

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    Looks like Fable is using Forzatech

    https://careers.microsoft.com/us/en/job/1039800/Software-Engineer-Turn10-Studios
     
  20. t0mb3rt

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    I remember seeing a test (can't remember what site or where I saw it) where they tested CU count scaling on RDNA 2 GPUs and found that they scale in performance pretty well up to 60 CU, but above that the scaling drops off dramatically.
     
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