I have 2 mains comments to the document. The shader should not be SIMD, most shader do not use vector operation. So on scalar code 3 out of 4 ALU will not be used. I think that nvidia is going from 2 way SIMD to scalar shader.
>From a previous study on shader code poster here, the shader looks like a cpu that should do an fmul per cycle, so LIW structure looks the best. The load/store unit is a complex one to handle all the type of data without any other cpu instructions (2D structure access, texture incoded in different color schem as Yuv or RGBA with different bits per channel). A NVIDIA paper spoke about 18 differents datatypes! The second comment is about the easyness about shader programming. Some game developer said that gpu programming is for more complex than there budget enable. They prefer to sacrifice performance against easyness of programming. Larrabee looks to meet this goal. But using 512 bytes vector is not so easy too ! On SOC system, it's common to use "accelerator" for different tasks (offload jpeg compressor, cryto DMA,...). But most of the time this unit are not flexible at all and it could be faster to do the job on the cpu to avoid communication! I prefer the idea to include specific instruction.It's far easier to use for the coder : communication are free, switching context are included. And this specific instruction, if they take one cycle are always faster than any other instruction combination. Larrabee use a specific instruction for the classical rasterisation. In that cases, the software should be written in the same time of the hardware to find the easiest way to acheive usable maximum performance. Usual shader are not the easiest path ! Regards, Nicolas 2009/9/14 Andre Pouliot <[email protected]>: > Hi everyone, > > The current work on OGA1 and OGD1 is still progressing. Not as fast as we > expected at first, but still going forward. > > With the experience we acquired working on OGA1, a small group of developer > started a specification for the next architecture revision of the open > graphics projects: The Open Graphics Architecture 2 (OGA2) > > That new revision will be with programmable shader that can also be use for > GPGPU. The current work document can be seen here: > http://docs.google.com/View?id=dfsp4qpd_41dtrrskfb > > As everyone can see, it's a work in progress. We welcome everyone to read > the specification and discuss, criticize and bring suggestions on OGML. > > If you have any question or comment on OGA2 we'll be happy to answer as best > as we can. > > André Pouliot > > _______________________________________________ > Open-graphics mailing list > [email protected] > http://lists.duskglow.com/mailman/listinfo/open-graphics > List service provided by Duskglow Consulting, LLC (www.duskglow.com) > _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
