It's not brand new, but I recently stumbled upon this and I must say it is a must read for anyone who is interested in (GCN) pipeline optimizaiton.
frostbite-wp-prd.s3.amazonaws.com/wp-content/...Posted Oct 2, 2018, 6:17 PM UTC
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thats one of the biggest reasons GCN is not meant for gaming gpus but data centers. you basically wanna run draw calls on the cpu 100% of the load. not calculate stuff on the GPU. all you want the gpu for is graphics and geometry and this stuff
AMD gpus just do unnecessary work because they are compute cards and the parts that draw and shade pixels are nerfed
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its not really the best way and thats why amd is dumping GCN after navi
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It's funny you say that, because deep dives on Turing seem to indicate that it's become a lot more 'gcn-like' than any Nvidia architecture before it, specifically because compute is literally the best way to handle more advanced and more realistic non-rasterization things like Ray-tracing. So.
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That's horrendously bad reasoning. AMD are doing something new thus the last thing was awful. Every single good cpu architecture has been replaced by a newer one, that doesn't mean every past cpu architecture sucked.
If GCN sucked and Pascal didn't, why was Pascal dumped?
GCN is old now, there is only so many iterations and improvements you can make to really any given architecture before both starting fresh makes sense and newer modern requirements changes how suitable an older architecture is for modern workloads.
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Nonsense, post Navi will almost definitly still be GCN as far as the drivers are concerned. They might change the internal ISA to VLIW to maximize perf/watt. But it would be almost a direct mapping to GCN otherwise except all the instruction decoding would be done in either hardware or specialized software and cached on chip. This is very similar to how all relevant x86 cpus work these days.
NVidia actually has some VLIW hardware out there today in their Denver and Carmel ARM cores .... and they are extremely efficient.
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Do you have any technical resources or data to show GCN is an untenable architecture for real-time graphics? I can't find an explanation that is low level enough to be convinced there's a fundamental problem unsolvable by software.
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yes. that fundamental problem is that the GCN cores are so large that there is no space for geometry engines. ROPs or TMUs . but thats not the main problem. the main problem is monetary issues.
ROPs are the units that take the pixels and render them to your screen. TMUs shade and rasterize the pixels. AMD cards always have significantly less of those than Nvidia because GCN cores leave no space for it
for example. if you have a data center card. you'd want 0 TMUs and zero ROPs. they are not useful for you. so AMD. instead of making seperate data center cards. and seperate Gaming cards. they had no money. so they drew a line in the sand to make hybrid cards
why do you think AMD vega 64 is all of the sudden way better at compute than a 1080 ti? because its a quasi Data center professional card.
they had no money to fab both . its unavoidable by software. because you can't possibly shade more pixels or fill in more pixels faster .
the RX 580 for example has 2304 : 144 : 32 . Cores TMUs, ROPS.
if TMUS and ROPs aren't a hardware bottleneck then lets look at the xbox one X gpu which is on paper an RX 580 except.
it has a lower clock. And on top of that. it has 160 TMUs instead of 144. and it has 32 ROPs but I don't think they had the chance to increase that due to how physically the chips are.
the PS4 pro gpu is a ~470. and it has 64 ROPs. why is that? because they need graphics power. not just compute power.
so it has double the rx 470 ROPs. and it has 144 TMUs compared to the 128 the 470 has.
ROPs and TMUs are far more reasons that will increase graphical performance than compute power.
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The RTX 2070 and Vega 64 both have 64 ROPs with comparable pixel rates at the same clock. For TMUs the Titan Xp is the closest comparison I can find with 240 vs 256 on Vega which has higher texture rates as I would expect.
The 1080 Ti does have 24 more ROPs but only about 30 GP/s higher pixel rate so there seems to be some diminishing returns on just raising the count? I'm not sure what would prevent adding more or increasing the throughput of the ones that are there.
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well you need to increase the clock which isn't always possible and has other effects. increasing the count means you get more graphical power at a lower pick. which is why the ps4 pro gpu runs at 911 MHZ.
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dont forget that the nvidea gpu are usually rated at much lower clocks than they actually work at, if you do the math with 2 ghz core clock the nvidea advantages in pixel fill rate will be obvious
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The Xbox One X and RX 580 are different designs. RX 580 tops out at 36 CUs, Xbox One X has 44 on-die, 40 enabled in the Xbox One X when it gets sold.
PS4 Pro has 36 CUs. Same as a 580. But the clocks are lower. And it has double-rate FP16 support.
Technically the Xbox One X is slightly different from Polaris, because of full DirectX 12.1 support. As opposed to "just" DirectX 12.0.
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thats a small difference am specifically talking about why you need ROPs and TMUs. you can't say "oh that gpu has 100 teraflops its the best gaming gpu"
that doesn't work.
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Make Rasterization Great Again!
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Thanks for posting. Good presentation, but it's worth pointing out that it's mainly about culling. Still, some interesting GCN details and a worthwhile read.
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since occlusion culling and frustum culling respectively are a main pillar of pipeline opt. this shouldn't come as a surprise. it's all about draw calls draw calls draw calls .... and the only prescription for it is batching and culling...
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Perhaps, but I think it's still worth pointing this out, because 'pipeline optimisation' doesn't necessarily bring this to mind, in particular in the age of DX12 style APIs, where pipeline dependency optimisation became a thing. That in my mind is 'pipeline optimisation', getting the pipeline to function smoothly.
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Meanwhile most data centers only use CUDA. The only “computing “ GCN is good for is crypto mining. We have multiple generations of AMD GPUs frequently used for mining now.
GCN had its glory days. Time for it to be put down now.
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Just give it up already, enjoy your 2080 or w/e you own and hang around r/nvidia instead of shitposting all over r/amd.
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Sorry my main drive is a FuryX. This is why I know GCN sucks.
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jaxkrabbit 5 days ago
At least I didn’t have FineWine on my FuryX. No Async Reprojection support until this day. And regression in VR performance for every driver after 18.5.1. Oh well i am moving onto a cheap 1080Ti i just scored on EVGA store so guess it is goodbye to RTG then.
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So? I used FuryX for 3 years and more than eligible to criticize the experience first hand.
This is why toxic crazy fans are ruining AMD. GCN sucks, face it. That is also exactly why they are ditching GCN. Same as bulldozer, Company puts out shitty products and they get what they put out. Trying to cover it up does no one good.
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My favorite part about it