More RadeonSI Navi Improvements Are Pending

[skeevy420]

My 1000th post

[skeevy420]

Thank you!

Yet, if it's an API thing, why does an AMD representative say it's not coming for GFX9 but the next arch (NAVI)?

https://www.mail-archive.com/amd-gfx.../msg24458.html

Perhaps it's a "get it working on the new stuff and backport when that's done" situation?

[skeevy420]

I'm still a bit confused as I don't understand why Fiji/Tonga is separated from Polaris in the new naming scheme if AMD considers them the same generation.

3-1/2th maybe ?

It programs like a 3rd generation part other than a single register bit, but a number of the HW blocks changed to improve performance and save power. From a marketing POV it is reasonable to call it a 4th generation part while from a driver perspective it's still GFX8.

Scroll up? While that's about Polaris, it does answer your question.

[entropy]

For historical reasons there are multiple separate stages (vertex, tesselation, geometry shader) that have to be run before a primitive can be culled or rasterized. Primitive shaders merge these stages and make culling programmable, which allows for early/optimized culling to reduce the number of primitives processed.

The problem is that this merged shader has to somehow exposed by the API to users. And that is something they are probably struggling with, getting it into directx/vulkan.

Thank you!

Yet, if it's an API thing, why does an AMD representative say it's not coming for GFX9 but the next arch (NAVI)?

https://www.mail-archive.com/amd-gfx.../msg24458.html

[log0]

Can somebody please explain in simple words what those Primitive Shader / NGG actually are for?

From what I read (might got that completely wrong) it is meant to be an early shader
stage that allows culling and discarding stuff early and much more efficiently. (?)

...

For historical reasons there are multiple separate stages (vertex, tesselation, geometry shader) that have to be run before a primitive can be culled or rasterized. Primitive shaders merge these stages and make culling programmable, which allows for early/optimized culling to reduce the number of primitives processed.

The problem is that this merged shader has to be somehow exposed by the API to users. And that is something they are probably struggling with, getting it into directx/vulkan.

[entropy]

Can somebody please explain in simple words what those Primitive Shader / NGG actually are for?

From what I read (might got that completely wrong) it is meant to be an early shader
stage that allows culling and discarding stuff early and much more efficiently. (?)

What's the other part of the story?

Is this a feature that will be a base part of Vulkan and D3D12 and, thus,
something all vendors will implement or is this some AMD speciality (for now)?

So AMD promised that feature for VEGA but could not deliver and now people are speculating
what the reason is? Hardware bugs, software issues, whatever..?

Will NAVI feature NGG?

Thanks!

[societaleclipse]

Yep, agreed... we briefly tried going along with the naming conventions the tech media were using (1,2,3 / 1.0, 1.1, 1.2 etc...) but found it just as confusing.

Internally we talk about GFX6 (SI), GFX7 (CI), GFX8 (VI incl. Polaris), GFX9 (Vega), GFX10 (Navi) etc... but in all cases that is only talking about the graphics core, not any of the other HW blocks on the chip.

I'm still a bit confused as I don't understand why Fiji/Tonga is separated from Polaris in the new naming scheme if AMD considers them the same generation.

[bridgman]

Really annoying, yet understandable, that they revised the numbering scheme. I had a 1.1 and it suddenly became 2 making info a bit difficult to search for.

Yep, agreed... we briefly tried going along with the naming conventions the tech media were using (1,2,3 / 1.0, 1.1, 1.2 etc...) but found it just as confusing.

Internally we talk about GFX6 (SI), GFX7 (CI), GFX8 (VI incl. Polaris), GFX9 (Vega), GFX10 (Navi) etc... but in all cases that is only talking about the graphics core, not any of the other HW blocks on the chip.

[skeevy420]

3-1/2th maybe ?

It programs like a 3rd generation part other than a single register bit, but a number of the HW blocks changed to improve performance and save power. From a marketing POV it is reasonable to call it a 4th generation part while from a driver perspective it's still GFX8.

Marketing calls it a 4.

Really annoying, yet understandable, that they revised the numbering scheme. I had a 1.1 and it suddenly became 2 making info a bit difficult to search for.

[skeevy420]

Polaris is 3rd or 4th GCN?

3rd under the old/original naming scheme and 4th under the new/revised naming scheme.

GCN Versions
old   new
1.0   1  (SI enabled for AMDGPU else radeon)
1.1   2  (CIK enabled for AMDGPU else radeon; Bonaire/Hawaii)
2     3  (this and below are all AMDGPU only; Tonga/Fiji)
3     4  (revised naming scheme; Polaris/VegaM)
      5  (last GCN version; Vega)

RDNA
1  (Navi)