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> And worse, different binary slices are used between different dies of the same product line. As an example, for RDNA2, ROCm math libraries are compiled only f

by paulmd 4y ago

> And worse, different binary slices are used between different dies of the same product line. As an example, for RDNA2, ROCm math libraries are compiled only for Navi21. This means that on a (smaller) Navi22 die (notably present in the 6700 XT), those components aren’t functional. The workaround is manually recompiling ROCm with support for more targets. Such a roadblock is very discouraging for adopters – and does complicate application distribution too. holy shit I didn't realize the portability story was that bad, it can't even target a whole uarch/family at once (eg target all RDNA2) and it has to know about every specific die it will ever run on? yeah I mean that's the deep deep problem with ROCm is there's no equivalent to PTX, AMD just wants you to distribute source and recompile everything at runtime, everything about ROCm pushes you towards source distribution rather than any kind of bytecode/IL or gosh even an executable file you could actually just run. On NVIDIA the support story is simple: the driver does the final translation from PTX to assembly at runtime, so, as long as there is at least one overlap in the PTX versions packaged in the app and the PTX versions supported by the driver, it runs. In practice this means you can take a program that was compiled for a CUDA 1.0 GPU (tesla uarch) and it'll run today on an ada, no questions asked. You might be leaving performance on the table by not fully exploiting the newer uarchs, but it'll run, just like x86. And you can take a program today and compile it against CUDA 1.0 capability targets (as long as it doesn't use any features that don't exist in those older versions) and the full 2023-era software toolchain will all just magically work on your 8800GTX even though driver support for that hardware has been dead for 10+ years. Because the driver knows how to run PTX 1.0 and the toolchain knows how to build PTX 1.0, and that's all that matters. ROCm has always really struck me as being aimed at the HPC market - only supporting pro-tier GPUs, focusing on users who are already running custom software, openly disdaining amateur support, etc. And frankly the distribute-as-source model makes ROCm just a complete nonstarter for any sort of commercial or other model where the vendor would absolutely be distributing libraries or a compiled application, let alone trying to wrangle dumb customers through getting a working ROCm environment. Which right now is the authentic "linux in 1995" level experience/ordeal. Getting serious would be restarting the GPU Ocelot project and going after PTX compatibility. But a corporation is never going to accept being a client on someone else's platform, just like they won't support the open-source Streamline framework because something something 'pluggable frameworks and library code are anti-user-freedom'. Same thing there too, AMD will only support FSR in statically-compiled code and they expect everyone to recompile all their shit and validate and push updates for every single game, every time AMD releases an update, because it's inconvenient for AMD's corporate strategy. https://youtu.be/8ve5dDQ6TQE?t=974 https://youtu.be/8ve5dDQ6TQE?t=974 (oh and now that they finally have the ML hardware, the rumor is they're working on their own ML-based upscaler, quelle surprise that the "gosh we would never do anything that legacy users couldn't run" was just a bit too.) AMD doesn't want user freedom, they want to be the one with the leash. That's why they do the source-distribution-only model... you'll have to work with your code in the ROCm ecosystem and not NVIDIA's. You'll be compiling against HIP and not NVIDIA's stuff. Etc etc. It's not a zero-effort thing to leap the gap, and they want to keep you once you do it, you'll have the same leap to get back out.

JonChesterfield 4y ago
It's more subtle than that. AMDGPU doesn't have an equivalent to PTX to abstract over differences between hardware generations. So while CUDA caused problems with Volta changing the intrinsics it was able to mostly paper over it in the toolchain. For AMDGPU, changing from a gfx1030 to a gfx1031 probably means recompiling all the machine code. Because there are _lots_ of different cards and they all have their own machine code, distributing libraries is a pain. You either distribute N copies or do some packaging effort to hide that you've distributed N copies, or you ship raw LLVM IR and cross your fingers that patching it up on the fly works out, in defiance of LLVM not really supporting that. AMD as a company is in favour of open source. How they feel about user freedom is less obvious, but as long as I can rebuild their stack from source when it falls over, I'm going to stick with it over nvidia. I especially like that the driver ships in the linux kernel.
- paulmd 4y ago
  I don't know man, did you watch the video I linked from AMD's FSR lead? "we won't support [an open source API/framework] because it might be used to plug things we don't like" is pretty explicitly hostile to both user freedom and open source as a whole. The freedom to do things that you might not want me to or that you won't do is really the only user freedom in this sense, right? What happens when some game won't update to FSR 2.2 and you're stuck on FSR 2.1 forever? That's the thing open-source user freedom is supposed to fix, right? AMD doesn't get to determine that "our software is the best and alternatives offer no benefits" either, that's the end-user's choice, and when that's followed by "therefore we will work against adoption of pluggability and interoperability standards" that crosses into openly hostile. The lead is being very diplomatic and careful but that's a very coached way to say that "this interoperability standard isn't good for us and we will work to kill it and prevent adoption, regardless of its open-source nature. Our product is better than theirs and we are going to work to deny you the freedom to choose otherwise." That's some microsoft level embrace-extend-extinguish shit right there: this is them embracing upscaling tech, extending it with their own proprietary implementation and deliberately kneecapping interoperability, with the goal of eventually extinguishing DLSS. They're just saying the quiet bit out loud and generally being delusional to think they could ever make this happen. -- Look, big-picture here: AMD did the open-source driver on linux thing because it was a way to get a force-multiplier on their dev time - the community does the work instead of employees that AMD has to pay for. It's a niche community with a DIY mentality and AMD (and Intel before them) leaned on that to get more work done. AMD's not open-sourcing drivers on Windows. They slap down open APIs like Streamline when it doesn't support their business strategy. The same thing is happening with ROCm - everyone else does software this way, but, AMD wants you to do it that way, even though it's more work and more cumbersome for end-users, because it results in more lock-in for their software ecosystem. Is that not fundamentally the same thing as people accuse NVIDIA of doing? And that's how they've handled FSR too - user freedom doesn't really matter that much as a principle, actually they've stated they're explicitly against users having these freedoms. They want people statically compiling it because if they embraced user freedom it would help users move more freely between these ecosystems and they don't want that, they are fine with lock-when you're locked into their ecosystem. What they mean by "user freedom" is they want to prevent users from plugging a library that interfaces with their competitor's hardware accelerators. That's actually the opposite of user freedom. And where does PSP fit into user freedoms - a whole closed processor running underneath your user experience doing god knows what? Wasn't that something people flipped an absolute fucking shit over with Intel ME? Yeah it's got closed-source elements that make it a problem to open, but isn't that also true of the NVIDIA drivers people constantly whinge about? What's the reason for giving AMD a pass on external IP but not NVIDIA? Blobs don't matter anymore if it's AMD? Or the platform lock - literally preventing secondhand resale of server cpus (and now desktop CPUs too) if they're ever used in a branded system. Note that it's not locked to a motherboard - it's not about preventing parts swapouts. It's locked to a brand, so you can swap any other HP-locked cpu into a HP-locked system. Clearly 100% targeted at killing the secondhand market, and that's pretty damn anti-user-freedom as well, why shouldn't I have the freedom to buy a used CPU if I want? Because it would impact AMD's bottom line I guess? Like, at the end of the day AMD is rolling in the anti-user-freedoms shit same as everyone else. It's a bit, when you're the underdog you need an angle to get people to buy you. When the incentives align and you and AMD are both seeing a benefit from the open-source strategy it's great, but it's not something they "are in favor of as a company", they're happy to say no to open-source when it gives them a strategic advantage.

by paulmd 4y ago

JonChesterfield 4y ago

It's more subtle than that. AMDGPU doesn't have an equivalent to PTX to abstract over differences between hardware generations. So while CUDA caused problems with Volta changing the intrinsics it was able to mostly paper over it in the toolchain. For AMDGPU, changing from a gfx1030 to a gfx1031 probably means recompiling all the machine code. Because there are _lots_ of different cards and they all have their own machine code, distributing libraries is a pain. You either distribute N copies or do some packaging effort to hide that you've distributed N copies, or you ship raw LLVM IR and cross your fingers that patching it up on the fly works out, in defiance of LLVM not really supporting that. AMD as a company is in favour of open source. How they feel about user freedom is less obvious, but as long as I can rebuild their stack from source when it falls over, I'm going to stick with it over nvidia. I especially like that the driver ships in the linux kernel.

paulmd 4y ago
I don't know man, did you watch the video I linked from AMD's FSR lead? "we won't support [an open source API/framework] because it might be used to plug things we don't like" is pretty explicitly hostile to both user freedom and open source as a whole. The freedom to do things that you might not want me to or that you won't do is really the only user freedom in this sense, right? What happens when some game won't update to FSR 2.2 and you're stuck on FSR 2.1 forever? That's the thing open-source user freedom is supposed to fix, right? AMD doesn't get to determine that "our software is the best and alternatives offer no benefits" either, that's the end-user's choice, and when that's followed by "therefore we will work against adoption of pluggability and interoperability standards" that crosses into openly hostile. The lead is being very diplomatic and careful but that's a very coached way to say that "this interoperability standard isn't good for us and we will work to kill it and prevent adoption, regardless of its open-source nature. Our product is better than theirs and we are going to work to deny you the freedom to choose otherwise." That's some microsoft level embrace-extend-extinguish shit right there: this is them embracing upscaling tech, extending it with their own proprietary implementation and deliberately kneecapping interoperability, with the goal of eventually extinguishing DLSS. They're just saying the quiet bit out loud and generally being delusional to think they could ever make this happen. -- Look, big-picture here: AMD did the open-source driver on linux thing because it was a way to get a force-multiplier on their dev time - the community does the work instead of employees that AMD has to pay for. It's a niche community with a DIY mentality and AMD (and Intel before them) leaned on that to get more work done. AMD's not open-sourcing drivers on Windows. They slap down open APIs like Streamline when it doesn't support their business strategy. The same thing is happening with ROCm - everyone else does software this way, but, AMD wants you to do it that way, even though it's more work and more cumbersome for end-users, because it results in more lock-in for their software ecosystem. Is that not fundamentally the same thing as people accuse NVIDIA of doing? And that's how they've handled FSR too - user freedom doesn't really matter that much as a principle, actually they've stated they're explicitly against users having these freedoms. They want people statically compiling it because if they embraced user freedom it would help users move more freely between these ecosystems and they don't want that, they are fine with lock-when you're locked into their ecosystem. What they mean by "user freedom" is they want to prevent users from plugging a library that interfaces with their competitor's hardware accelerators. That's actually the opposite of user freedom. And where does PSP fit into user freedoms - a whole closed processor running underneath your user experience doing god knows what? Wasn't that something people flipped an absolute fucking shit over with Intel ME? Yeah it's got closed-source elements that make it a problem to open, but isn't that also true of the NVIDIA drivers people constantly whinge about? What's the reason for giving AMD a pass on external IP but not NVIDIA? Blobs don't matter anymore if it's AMD? Or the platform lock - literally preventing secondhand resale of server cpus (and now desktop CPUs too) if they're ever used in a branded system. Note that it's not locked to a motherboard - it's not about preventing parts swapouts. It's locked to a brand, so you can swap any other HP-locked cpu into a HP-locked system. Clearly 100% targeted at killing the secondhand market, and that's pretty damn anti-user-freedom as well, why shouldn't I have the freedom to buy a used CPU if I want? Because it would impact AMD's bottom line I guess? Like, at the end of the day AMD is rolling in the anti-user-freedoms shit same as everyone else. It's a bit, when you're the underdog you need an angle to get people to buy you. When the incentives align and you and AMD are both seeing a benefit from the open-source strategy it's great, but it's not something they "are in favor of as a company", they're happy to say no to open-source when it gives them a strategic advantage.