Direct3D feature levels discussion

Metal_Spirit said:
Since there was no feature level defined above 11_1 at that time, I believe that was a claim for hardware support above that feature level. Like the support for Tiled resouces, a DX 11.2 feature (And we all know PS4 supports in hardware Partially Resident Textures).
Click to expand...
Unfortunately we don't know what tier level that is. It's never been confirmed and going with a GPU that heavily resembles Pitcairn puts them in a position to be GCN1.0 only. Meaning tier 1. If that is true by definition it won't be a FL12_0 because it's missing tier 2. A technicality that probably likely has no real performance impact in most titles, but since we are trying to bucket GPUs for the sake of discussion this should be noted.

Besides, the PS4 custom GPU has more than a passing resemblance with Vulcan Islands (GCN 1.1), sharing, at least, it´s GPGPU 8 ACES.
Click to expand...
I don't think that is a strong argument at all. It's like saying having more CUs is a sign of a higher GCN level which we see isn't true. Tonga has less bandwidth yet is GCN1.2 and all other GPUs like Hawaii are still GCN1.1.

Going by your thought process however we could claim that Xbox one is gcn1.2 (and I'll show you why we'd be wrong). In the SDK they refer to heavily leverage compressed depth and colour buffers for ROP efficiency, as well as a highly efficient GCP (architect interview indicates that this customization will find its way into the PC space). Not to mention the inclusion of resource binding tier 3 into dx12. All of these features are found in Tonga(-resource binding which it tier 2).

But Xbox is missing the inclusion of native 16bit instructions and I assume registers. So can we consider it really a GCN1.2?

Likely not.
But Xbox has resource binding tier 3 and so will Fiji. Does that make Xbox GCN1.3??

So when it comes to straight features GCN may not necessarily line up with Dx12 feature levels. Feature levels are just feature levels. R280 is Pitcairn IIRC. And Pitcairn is GCN1.0. But does that mean R280 has no tier 2 tiled resources?

How strange, cause I don't even know the answer to my own question.

So definitely we need to be careful how we line things up here.

TLDR; GCN levels are made up by journalists and not supported by AMD.

GCN != FL.
 
Last edited:
iroboto said:
Not to mention the inclusion of resource binding tier 3 into dx12. All of these features are found in Tonga(-resource binding which it tier 2).
Click to expand...

I thought it was already established that all GCN parts including 1.0 supported resource binding Tier 3?
 
Resource Binding Tier 3 support was assumed, it's based on the numbers MS quoted from Steam (Max McMullen said x% of current cards (based on Steam numbers) support resource binding tier 3, and all GCN's put together comes up to that % (can't really remember what the exact % was, but it's earlier in this thread))
 
17% I think. It'd be interestin to understand how many systems that equates to. Then double it to account for the Nvidia market, then add say another 10-15% for the none Steam market (if such a thing exists) and right there you have a rough idea of the size of the "console equivilent PC market".

I'm sure most developers are alrady quite familiar with that statistic!
 
Hey gang, as some of you may know the first public beta of the Win10 SDK is out. As you'd imagine, it includes an updated copy of the dxcapsviewer. Unfortunately Win10 at this time still does not have definitions for FLs newer than 11_1, so it's not possible to nail down FLs through dxdiag or dxcapsviewer.

However the latest version of the caps viewer does include a few more feature flags than previous versions, including some tier listings. Since I already have a Win10 test bed spun up for something else, I quickly grabbed the caps viewer output for the major AMD and NVIDIA archs.

http://images.anandtech.com/reviews/video/dx12/fls/GTX980.png
http://images.anandtech.com/reviews/video/dx12/fls/GTX680.png
http://images.anandtech.com/reviews/video/dx12/fls/GTX750Ti.png

http://images.anandtech.com/reviews/video/dx12/fls/290X.png
http://images.anandtech.com/reviews/video/dx12/fls/285.png
http://images.anandtech.com/reviews/video/dx12/fls/7970.png

(These are beta drivers on a not even beta OS, so as usual the standard disclaimers about results being subject to change do apply. Especially if not all features are currently being exposed in these drivers)

Whoever had GCN 1.0 at Tiled Resources Tier 1 and GCN 1.1 at Tier 2, please be sure to collect.
 
pjbliverpool said:
I've tried to summarise the results here although my knowledge is limited so I'm assuming a little on the Typed UAV and Resource Binding levels:



Anyone see any problems with this?
Click to expand...

According to this slide UAV slots should be higher than 64 (full heap) for Resource Binding Tier 3:

microsoft_directx_12_resource_binding_tiers.png

So, Resource Binding on GCN 1.0/1.1/1.2 should be Tier 2 not Tier 3. Am I right?
 
mosen said:
According to this slide UAV slots should be higher than 64 (full heap) for Resource Binding Tier 3:
So, Resource Binding on GCN 1.0/1.1/1.2 should be Tier 2 not Tier 3. Am I right?
Click to expand...
No you're not, since they said 17% of Steam has Resource Binding Tier 3 and only way to come up with that % is all of GCN's put together
 
It's worth noting that since Maxwell 1 lacks UAVs at every stage it also fails to meet FL11_1. So we can categorize the different architectures as follows:

Kepler/Maxwell 1: FL11_0
GCN1.0: FL11_1
GCN1.1/1.2 (and maybe consoles): FL12_0
Maxwell 2 (and almost certainly GCN1.3): FL12_1
 
pjbliverpool said:
It's worth noting that since Maxwell 1 lacks UAVs at every stage it also fails to meet FL11_1. So we can categorize the different architectures as follows:

Kepler/Maxwell 1: FL11_0
GCN1.0: FL11_1
GCN1.1/1.2 (and maybe consoles): FL12_0
Maxwell 2 (and almost certainly GCN1.3): FL12_1
Click to expand...
I know this might sound annoying, but could you spreadsheet out what we know and see for a buyers guide?
What if different architectures but refreshed like 280x is pitcairn GCN1.0, what if it has Tier 2 tiled resources? I think we need to label what we see. That way people are informed exactly on their card what features they should have.
If it's 64 reported for UAV, we should report it as such. It's 64 for 980, and it's 64 for 7970 - but we write out that one is tier 3 and one is tier 2. We're officially dirtying data.

I rather go off the obvious, which is what dxdiag is telling us than trying to reverse engineer numbers from a slide. One is bound to be more correct than the other. Since ultimately when DX12 is being used, it's going to use the values available from that DXDiag, and not the slide on GDC. The very last line of that DXDIAG - Note: This feature summary is derived from hardware feature level.

You may have to transpose your spreadsheet and have the features run along the top, and the video cards run straight down.
 
Last edited:
pjbliverpool said:
I've tried to summarise the results here although my knowledge is limited so I'm assuming a little on the Typed UAV and Resource Binding levels:



Anyone see any problems with this?
Click to expand...
Well, has that Tier 3 Tiled Resources been confirmed for Maxwell gen 2?
Also, wasn't there some talk about at least some GCN's supporting ROVs?
 
Kaotik said:
Well, has that Tier 3 Tiled Resources been confirmed for Maxwell gen 2?
Also, wasn't there some talk about at least some GCN's supporting ROVs?
Click to expand...
Look at Ryan's pictures :)

And this is exactly why we need to report what is there. Assumptions are going to kill us especially if the definitive version is what dxdiag says what it is.
 
Kaotik said:
No you're not, since they said 17% of Steam has Resource Binding Tier 3 and only way to come up with that % is all of GCN's put together
Click to expand...

So what? We know that (based on 2/15/2015 steam survey) 17% of DX12 market GPUs has RB Tier 3. The initial results from Steam survey which made by random people was based on some initial and likely incorrect assumptions.

Read this post and it's assumptions:
https://forum.beyond3d.com/posts/1829887/

pjbliverpool said:
I'm guessing full heap is simply reported as 64 UAV slots in dxcapsviewer.
Click to expand...

I don't think so. I can see "PS Specified Stencil Ref" in dxcapsviewer and also it shows "Tier 3" of Tiled Resource for Maxwell 2, so why should we assume that it shows "64" UAV slots instead of "full heap"?\
 
Last edited:
Agreed. No point for assumptions since what is provided in dxcapsviewer is better than any "guessing" this point in time. Time will tell if this holds up or if modification is required of dxcapsviewer.

Great idea Ryan!
 
mosen said:
So what? We know that (based on 2/15/2015 steam survey) 17% of DX12 market GPUs has RB Tier 3. The initial results from Steam survey which made by random people was based on some initial and likely incorrect assumptions.

Read this post and it's assumptions:
https://forum.beyond3d.com/posts/1829887/



I don't think so. I can see "PS Specified Stencil Ref" in dxcapsviewer and also it shows "Tier 3" of Tiled Resource for Maxwell 2, so why should we assume that it shows "64" UAV slots instead of "full heap"?\
Click to expand...

The best evidence I can find that all GCN parts support Tier 3 Resource Binding is this forum post:

http://forums.anandtech.com/showthread.php?p=37199507

It's just a post but it does seem to come from a knowledgeable source and later in the thread he does post links to the AMD source material (of which there is too much for me to go through right now).
 
iroboto said:
Look at Ryan's pictures :)

And this is exactly why we need to report what is there. Assumptions are going to kill us especially if the definitive version is what dxdiag says what it is.
Click to expand...
Ah, missed that part :oops:
 
You must log in or register to reply here.
Back
Top