Holy crap, memory barriers! It's a modern architecture that's finally caught up to where Symbolics was at in the '80s. Seriously though, this is good news for concurrent garbage collected languages.
AMD and ARM's new CPU/GPU virtual ISA
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Re: AMD and ARM's new CPU/GPU virtual ISA
#12Holy crap, memory barriers! It's a modern architecture that's finally caught up to where Symbolics was at in the '80s. Seriously though, this is good news for concurrent garbage collected languages.
Barriers are slow, and the more cores are hitting the barrier the slower it will be. The best news on that front was from the new GPU architecture parts, where they admitted that they're still going to expose the relaxed consistency memory model.
Re: AMD and ARM's new CPU/GPU virtual ISA
#13Wouldn't a virtual ISA be against the interests of hardware designers who benefit from ISA lockin?
Intel and NVidia want large piece of small pie AMD and ARM want small piece of large pie
Even NVIDIA isn't crazy enough to try to get everyone to use the same ISA again; they're trying to get you to buy into their compiler chain, not into the architecture of a particular generation of GPU.
Re: AMD and ARM's new CPU/GPU virtual ISA
#14Does this portability compromise performance at all?
Re: AMD and ARM's new CPU/GPU virtual ISA
#15Earlier quoted context omitted.
Intel and NVidia want large piece of small pie AMD and ARM want small piece of large pie
Even NVIDIA isn't crazy enough to try to get everyone to use the same ISA again; they're trying to get you to buy into their compiler chain, not into the architecture of a particular generation of GPU.
Is PTX really ISA?
It's also virtual, but very limited ...
Unlike PTX, FSAIL will work on both CPUs and GPUs and even will allow system calls from discrete GPUs.
Re: AMD and ARM's new CPU/GPU virtual ISA
#16Wouldn't a virtual ISA be against the interests of hardware designers who benefit from ISA lockin?
It would but none of the players have the mindshare, capital or cred to do this. We are at a near perfect astable state in terms of competition. I am really stoked about all of this.
One word. Microsoft, if them AMD and ARM are onboard that's it. Remember nVidia is an ARM licensor/developer
Re: AMD and ARM's new CPU/GPU virtual ISA
#17The part where they mention graphics becoming pre-emptable kinda solves Microsoft's concerns about WebGL DOS attacks.
Re: AMD and ARM's new CPU/GPU virtual ISA
#18I wonder if Apple will use this with Grand Central?
It wouldn't be hard, except for Apple being in bed with Intel.
As they exist today, GCD/libdispatch blocks are very similar to OpenCL native kernels, but with more automatic scheduling and implicit data transfers (which are almost no-ops when the kernel is running on the host device).
On an AMD Fusion system with a shared memory controller, you don't have the huge latency of transferring your kernel arguments to the GPU (and with libdispatch blocks, you are generally transferring less data), so a block could be executed on the GPU with hardly any more overhead than on a different CPU core.
The only problem would be that you would need universal binaries of your blocks to also target the GPU (or LLVM IR to be finalized at runtime). As Apple has complete control over their very modern and flexible LLVM-based toolchain, implementing this would be very straightforward, even without the fruits of an AMD/ARM collaboration. (Though it sounds like ARM may help AMD be able to provide an array of scalar processors that would have good performance characteristics for typical dispatch_async uses.)
Re: AMD and ARM's new CPU/GPU virtual ISA
#19Does this portability compromise performance at all?
It compromises performance in a similar way to using any byte code vs final machine code. It remains to see how much of a VM support will be required to make this work, as that's typically the large overhead cost of using non-machine code.
If anything the same exact FSAIL will run faster and faster on the same exact hardware as newer JITs come out.
Re: AMD and ARM's new CPU/GPU virtual ISA
#20Earlier quoted context omitted.
It would but none of the players have the mindshare, capital or cred to do this. We are at a near perfect astable state in terms of competition. I am really stoked about all of this.
One word. Microsoft, if them AMD and ARM are onboard that's it. Remember nVidia is an ARM licensor/developer
AMD is definitely not on board with Microsoft taking over the scene. AMD is 100% behind standards, standards like OpenCL. Look at the way MS implemented their AMP C++ GPU story, http://herbsutter.com/2011/06/16/c-amp-keynote/ that looks to me like it targets and has all the limitations of DirectCompute (MS specific GPGPU). If MS really wants to make this a standard then most likely AMD will implement that standard using Open64 (http://www.open64.net/) and emit OpenCL kernels which will be handed off to their device specific OpenCL compilers.
I don't think MS has the power you give it credit for.