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Intel Xe-LP GPU Architecture Deep Dive

50 points by m3at 6y ago

pjmlp 6y ago
> The downside is that it also means that Intel is the only hardware vendor launching a new GPU/architecture in 2020 without support for the next generation of features, which Microsoft & co are codifying as DirectX 12 Ultimate. The consumer-facing trade name for feature level 12_2, DirectX Ultimate incorporates support for variable rate shading tier 2, along with ray tracing, mesh shaders, and sampler feedback. And to be fair to Intel, expecting ray tracing in an integrated part in 2020 was always a bit too much of an ask. But some additional progress would always be nice to see. Plus it puts DG1 in a bit of an odd spot, since it’s a discrete GPU without 12_2 functionality. Not really on a good starting foot.
- the8472 6y ago
  If it supports GVT-g like their integrated graphics then it may still be useful as a cheaper alternative for virtualized systems. Otherwise you either have to buy multiple GPUs or the professional lines of AMD/Nvidia
- gigatexal 6y ago
  meh. Ray tracing is hype. I don't think it's omission is that big of a deal.
  - kevingadd 6y ago
    It's in all the next-gen consoles and in most of nvidia's current parts and (afaik) in all of amd and nvidia's future parts. At this point instead of a hyped up vendor-specific feature, it's looking like a feature many games will be using which will leave intel users out in the cold. On the other hand, nobody presently expects to run modern games on integrated GPUs, so... Some other 12_2 features are pretty important for VR.
  - pjmlp 6y ago
    Hollywood is of a different point of view. https://home.otoy.com/ https://home.otoy.com/ https://www.disneyanimation.com/technology/innovations/hyperion https://www.disneyanimation.com/technology/innovations/hyper... Also a standard feature of PS 5 and XBox Series X.
    - gigatexal 6y ago
      The price premiums for hardware with ray tracing hardware is still high and only when it becomes common place so as to not command a higher price will your average gamer care. There’s also always the next gen for Intel to add it.
    - erk__ 6y ago
      Neither of those are for realtime though. Ray tracing have been used in rendering for animations and movies a lot.
  - awalton 6y ago
    Real-time ray tracing is hype. And I agree - any arguments that "the next gen consoles have it" is specious at best; they always front load next gen consoles because there's usually a very, very long tail where they're essentially obsolete PCs but companies still have to churn out games for them. The PS4 was released in early 2013 - that's seven years, or almost 5 Moore generations old. The games released with RTRT right now are not going to be great, but in three years? Probably showing up in AAA titles, and they'll all be designed around the PS5's level of capabilities. But by then Intel will have revved their graphics card to the next generation (as will everyone else), and all of the "hardcore" gamers will be picking up new graphics cards anyways. That said, there are plenty of reasons to be skeptical of Intel's hardware's capabilities and priorities given how much they're trying to spackle the gap between being a server ML/NN play and a gaming device, their complete and utter management failures towards non-core market hardware (Intel's history is paved in abandoned hardware, up to and including the Xeon Phi) and them having little to no decent experience delivering SPMD programming models for their hardware as is now 100% bog standard in GPU land...
- ENOTTY 6y ago
  Not many people are going to be playing high-end games on the integrated graphics anyways, even with 2x performance improvement over the previous generation Intel graphics. At this point, the Xe graphics are going to be just slightly better than the recently released AMD APU integrated graphics. If this limitation is still true on their discrete card targeted for gamers (not the DG1), then that would be a poor showing.
  - pjmlp 6y ago
    Those buying P5 and XBox Series X games will.
    - aspaceman 6y ago
      Huh? I wouldn’t call AMDs architecture integrated. It’s a UMA with a discrete GPU. The most analogous thing is a laptop with a very nice GPU.
dragontamer 6y ago
CPU cores are pretty much a done deal IMO (unless Nuvia's hype is real. I guess we'll see about that soon). For the last 10, maybe 20 years, CPUs have simply grown bigger and have more or less done the same features. CPUs simply push wider SIMD (SSE -> AVX -> AVX512), bigger out-of-execution buffers, larger registers, deeper branch prediction, more cache. The biggest advancement seemed to be Intel's uop-cache in Sandy Bridge (a concept that was first tried in the Pentium4, so not really a "new" innovation). Even ARM chips are more of the same. Wider SIMD (see A64fx: #1 supercomputer in the world for 512-bit SVE), deeper out-of-order execution, better branch prediction. Its rare to see something new ---------- In contrast, whenever I see GPU-architectures, everything is so hugely different. True, GPUs all have a "SIMD focus", but there's so many exciting things about SIMD that just haven't been explored yet. NVidia has Tensor-cores, Raytracing cores. It was already crazy that NVidia had a full matrix-multiplication implemented in its FP16 processor in Volta, but Ampere is now pushing sparse matrix multiplication at the chip level (!!). AMD GCN and RDNA push GPU/SIMD architecture in a different direction. While a chunk of RDNA can be described as "more of the same", the "SubVector execution" feature grossly changes how Wave64 wavefronts are executed to save on register space and potentially have a better memory access pattern. Innovation continues in the AMD space for sure. Intel finally enters with their GPU / SIMD architecture, and they start of with... SIMD8 + SIMD2 (instead of the Wave32 of RDNA/NVidia or Wave64 for GCN). Finally, Intel is minimizing hardware scheduling (saving on die area), and focusing on software to schedule the instructions. Three very, very different architectures. Three very different ideologies for how SIMD compute / GPUs should be built. The SIMD / GPU architecture space remains more innovative than the CPU-architecture space by a longshot. Its exciting to see. -------- I'm not saying that CPU-advancements are dead per se. AMD did make chiplets a hot commodity (but chiplets were already experimented with Power5, and chiplets seem like a natural evolution to dual-socket or NUMA architectures... just cheap enough for a consumer now). Intel's new Tremont Atom core has this cool "dual-decoder" design (where one decoder works on one-branch, and the 2nd decoder works on a 2nd branch in parallel). There are certainly new ideas being tested in the CPU world. But nothing as majorly game changing as what Intel / AMD / NVidia are doing to the GPU space. (Or Google if we include TPUs in the discussion. A TPU isn't SIMD, but it shares some degree of similarity, especially to NVidia's Tensor cores) I guess big.LITTLE (and Intel's Lakefield platform) was a big change in the last 10 years. But that hasn't really seen much success in the Desktop/Server markets.

50 points by m3at 6y ago

> The downside is that it also means that Intel is the only hardware vendor launching a new GPU/architecture in 2020 without support for the next generation of features, which Microsoft & co are codifying as DirectX 12 Ultimate. The consumer-facing trade name for feature level 12_2, DirectX Ultimate incorporates support for variable rate shading tier 2, along with ray tracing, mesh shaders, and sampler feedback. And to be fair to Intel, expecting ray tracing in an integrated part in 2020 was always a bit too much of an ask. But some additional progress would always be nice to see. Plus it puts DG1 in a bit of an odd spot, since it’s a discrete GPU without 12_2 functionality. Not really on a good starting foot.

the8472 6y ago
If it supports GVT-g like their integrated graphics then it may still be useful as a cheaper alternative for virtualized systems. Otherwise you either have to buy multiple GPUs or the professional lines of AMD/Nvidia
gigatexal 6y ago
meh. Ray tracing is hype. I don't think it's omission is that big of a deal.
- kevingadd 6y ago
  It's in all the next-gen consoles and in most of nvidia's current parts and (afaik) in all of amd and nvidia's future parts. At this point instead of a hyped up vendor-specific feature, it's looking like a feature many games will be using which will leave intel users out in the cold. On the other hand, nobody presently expects to run modern games on integrated GPUs, so... Some other 12_2 features are pretty important for VR.
- pjmlp 6y ago
  Hollywood is of a different point of view. https://home.otoy.com/ https://home.otoy.com/ https://www.disneyanimation.com/technology/innovations/hyperion https://www.disneyanimation.com/technology/innovations/hyper... Also a standard feature of PS 5 and XBox Series X.
  - gigatexal 6y ago
    The price premiums for hardware with ray tracing hardware is still high and only when it becomes common place so as to not command a higher price will your average gamer care. There’s also always the next gen for Intel to add it.
  - erk__ 6y ago
    Neither of those are for realtime though. Ray tracing have been used in rendering for animations and movies a lot.
- awalton 6y ago
  Real-time ray tracing is hype. And I agree - any arguments that "the next gen consoles have it" is specious at best; they always front load next gen consoles because there's usually a very, very long tail where they're essentially obsolete PCs but companies still have to churn out games for them. The PS4 was released in early 2013 - that's seven years, or almost 5 Moore generations old. The games released with RTRT right now are not going to be great, but in three years? Probably showing up in AAA titles, and they'll all be designed around the PS5's level of capabilities. But by then Intel will have revved their graphics card to the next generation (as will everyone else), and all of the "hardcore" gamers will be picking up new graphics cards anyways. That said, there are plenty of reasons to be skeptical of Intel's hardware's capabilities and priorities given how much they're trying to spackle the gap between being a server ML/NN play and a gaming device, their complete and utter management failures towards non-core market hardware (Intel's history is paved in abandoned hardware, up to and including the Xeon Phi) and them having little to no decent experience delivering SPMD programming models for their hardware as is now 100% bog standard in GPU land...
ENOTTY 6y ago
Not many people are going to be playing high-end games on the integrated graphics anyways, even with 2x performance improvement over the previous generation Intel graphics. At this point, the Xe graphics are going to be just slightly better than the recently released AMD APU integrated graphics. If this limitation is still true on their discrete card targeted for gamers (not the DG1), then that would be a poor showing.
- pjmlp 6y ago
  Those buying P5 and XBox Series X games will.
  - aspaceman 6y ago
    Huh? I wouldn’t call AMDs architecture integrated. It’s a UMA with a discrete GPU. The most analogous thing is a laptop with a very nice GPU.

dragontamer 6y ago

CPU cores are pretty much a done deal IMO (unless Nuvia's hype is real. I guess we'll see about that soon). For the last 10, maybe 20 years, CPUs have simply grown bigger and have more or less done the same features. CPUs simply push wider SIMD (SSE -> AVX -> AVX512), bigger out-of-execution buffers, larger registers, deeper branch prediction, more cache. The biggest advancement seemed to be Intel's uop-cache in Sandy Bridge (a concept that was first tried in the Pentium4, so not really a "new" innovation). Even ARM chips are more of the same. Wider SIMD (see A64fx: #1 supercomputer in the world for 512-bit SVE), deeper out-of-order execution, better branch prediction. Its rare to see something new ---------- In contrast, whenever I see GPU-architectures, everything is so hugely different. True, GPUs all have a "SIMD focus", but there's so many exciting things about SIMD that just haven't been explored yet. NVidia has Tensor-cores, Raytracing cores. It was already crazy that NVidia had a full matrix-multiplication implemented in its FP16 processor in Volta, but Ampere is now pushing sparse matrix multiplication at the chip level (!!). AMD GCN and RDNA push GPU/SIMD architecture in a different direction. While a chunk of RDNA can be described as "more of the same", the "SubVector execution" feature grossly changes how Wave64 wavefronts are executed to save on register space and potentially have a better memory access pattern. Innovation continues in the AMD space for sure. Intel finally enters with their GPU / SIMD architecture, and they start of with... SIMD8 + SIMD2 (instead of the Wave32 of RDNA/NVidia or Wave64 for GCN). Finally, Intel is minimizing hardware scheduling (saving on die area), and focusing on software to schedule the instructions. Three very, very different architectures. Three very different ideologies for how SIMD compute / GPUs should be built. The SIMD / GPU architecture space remains more innovative than the CPU-architecture space by a longshot. Its exciting to see. -------- I'm not saying that CPU-advancements are dead per se. AMD did make chiplets a hot commodity (but chiplets were already experimented with Power5, and chiplets seem like a natural evolution to dual-socket or NUMA architectures... just cheap enough for a consumer now). Intel's new Tremont Atom core has this cool "dual-decoder" design (where one decoder works on one-branch, and the 2nd decoder works on a 2nd branch in parallel). There are certainly new ideas being tested in the CPU world. But nothing as majorly game changing as what Intel / AMD / NVidia are doing to the GPU space. (Or Google if we include TPUs in the discussion. A TPU isn't SIMD, but it shares some degree of similarity, especially to NVidia's Tensor cores) I guess big.LITTLE (and Intel's Lakefield platform) was a big change in the last 10 years. But that hasn't really seen much success in the Desktop/Server markets.