Where are detailed specs of PowerVR SGX

[maciek_urbanski]

Anyone has behavioral specifications, register maps ? (In my day job I'm optimizing graphics-intensive algorithms so I'm curious).

Is OGL driver open sourced ? And if yes - where is it ?

 

[mkinzler]

http://www.imgtec.com/powervr/sgx.asp

 

[maciek_urbanski]

http://www.imgtec.com/powervr/sgx.asp

Not true - this is just marketing talk. I'm interested in 'guts' - in short all information necessary to write/optimize OGL driver.

 

[mkinzler]

They provide an OpenGL ES 2 Emulation including libs and examples

 

[lardman]

There were also some more technical details on the Ti website: http://focus.ti.com/lit/ug/spruff6b/spruff6b.pdf

 

[WhyKlef]

I'm not aware of programming/developing and such but from the numbers I see, this little beast could do some serious 3D graphics. Although, It's sharing ram with the 128mb on board right?

 

[mkinzler]

It's sharing ram with the 128mb on board right?

Yes, but it hasn't a z-Buffer

 

[WhyKlef]

I've googled that z-Buffer of yours and quite frankly, I'm not sure if not having it is a good thing or not. I'd be saying that it's not good although z-buffering seems very demanding and buggy but what about optimization?

Unless what you meant is that the z-buffering will be handled by the GPU leaving a big chunk of the ram free to do other graphics operation but if that would be the case, that would mean that the GPU unit has it's own ram for the matter doesn't it?

Which therefore pretty much answers my question, my understanding: z-Buffering won't be possible :wacko:

 

[mkinzler]

PowerVR uses Tile Accelerating an type of deferred rendering. Thhus no (global) z-Buffer is needed. So it needs less memory and deferred rendering is alos faster then a z-buffer.

 

[WhyKlef]

I see, thanks for clearing that out for me! :lol:

 

[maciek_urbanski]

The funny fact is that after reading scraps of information available on the web and in PowerVR SDK it seem to me that OGL ES is in fact limiting the capabilities of SGX.

Most trivial example is Geometry Shaders. SGX Supports geometry generation in HW but GS is not part of of OGL ES core.

On OGL [non-ES] it's supported via GL_EXT_geometry_shader4 extension (implemented in NVidia & ATI drivers).

So, do we know what extensions supports PowerVR OGL ES driver ?

 

[mkinzler]

GS are introcuded with DY10/OpenGL 3. Dx10.1 is just possible with higher classes of SGX

 

[maciek_urbanski]

GS are introcuded with DY10/OpenGL 3. Dx10.1 is just possible with higher classes of SGX

...what in fact does not answer my question... :wink:

...and is only partially true. OpenGL 3.0 does not support geometry shaders directly, only through extension.

See:
http://www.khronos.org/news/press/relea ... ations_of/
http://www.opengl.org/registry/specs/AR ... hader4.txt

 

[yosh64]

hey

You might be interested in the OpenGL ES (Embedded Systems) specs, API and such.

edit
So to answer ya question (at least I hope it will), check the OpenGL ES Extension Registry.

another edit
I think it would be pretty safe to say it would support all the extensions with the prefix GL_OES, well some of these might be part of OpenGL ES 2.0 specs now.

and another...
Also look for gl.h and glext.h with the POWERVR sgx SDK (I assume they would exist), ya should beable to figure out what extensions are supported from these, so I thinks anyhows.

cyas

 

[warmi]

What do you mean it has no Z-Buffer ?

Of course it does ...

 

[drkIIRaziel]

PowerVR keeps an small internal Color, Stencil and Z buffer to hold one tile.After it is done processing one tile, the color buffer is stored to the ram and the next tile gets processed.If the code does not clear the z/stencil buffer PowerVR may be forced to also store the Z buffer to the ram after processing the image (this is quite not optimal for the hardware, and thats why its always suggested to clear the Z/Stencil buffers).

PowerVR gets limited from the opengl api -- the internal architecture is quite different than the one opengl exposes.As long as you follow the rules on the PowerVR sdk docs (you can register for free to get the sdk, it also contains a gl |es 2 emulator for pc-based development) performance will be good

 

[mkinzler]

If the TA-API would be directly supported, it would be easier to port dc games and stuff; let's wait and see

 

[maciek_urbanski]

...PowerVR gets limited from the opengl api -- the internal architecture is quite different than the one opengl exposes...

That's exactly my feeling. It would be great to get some internal documentation on SGX and program it directly (or create very lightweight API) to expose all HW capabilities and get more performance... Not very much unlike AMD/ATI's CTM(link).

Negative side effect would be that applications programming SGX directly would be harder to port to other architectures.

But it would allow to push HW to the limit creating some spectacular games - what could create abundance of good press and move Pandora more into the 'mainstrem' (or more precisely - move 'mainstream' closer to Pandora :wink.

 

[maciek_urbanski]

I've registered into PowerVR Insider Program and asked on their forum (and via e-mail) for those docs.

Keep your fingers crossed.