Hey don't forget who the poster is, Old hit and run Thunderdud himself. Too bad he didn't get the post from the same article who posted from about the author being totally wrong in what he was saying about Larrabee and how easy it will be to work with such a processor.
"by rauxbaught August 5, 2008 6:09 PM PDT As a long-time professional graphics programmer (who doesn't work for Intel), I can assure you that you are completely missing the point.
But before I get into that, let me correct a few complete fallacies in your article:
- There is no "reuse of information" across frames in video games. They took spaced out their samples because neighboring frames tend to be very similar. They wanted varying data points to determine the effect of varying loads on the various subsystems, and measure the scaling of the system as they add extra cores -- not to do sustained throughput measurements.
- Running multiple threads on a single core in in-order processors is generally done to cover memory latency. (This is different from out-of-order processors, which can have many more sequential instructions in flight at once, and use complicated logic to keep as many units as possible busy.) Hyperthreading in this case therefore increases the practical throughput of the system, since it's designed for parallelism instead of single-stream throughput.
- The use of 1Ghz cores was used to keep the math simple. (As was mentioned in the paper.) As far as we know, they could be using cores that run 2-3 times that frequency. (Or even half, for that matter...) Considering we don't know the frequency or the core count of their final hardware, comparing it to 2 year old hardware from nVidia is far from meaningful. (Thus making your claim that they won't be competitive very premature.)
- Binning (similar to previous techniques such as tiling) reduces the memory bandwidth to the framebuffer, not the polygons. If you'd read the paper, you'd see that their analysis indicates a significant memory bandwidth advantage over forward rendering, and memory bandwidth often predicts performance in graphics. As a side note, their algorithm is actually slightly different from traditional tiling techniques, which is presumably why they used different terminology.
Now, as for completely missing the point: They implemented everything in software. The very fact that they could contrast an immediate mode renderer against "binning" is a testament to how important Larrabee is as a paradigm shift. The performance balance of graphics development is currently determined by the hardware manufacturers. This has side effects like flat-shaded polygons being completely bound by numbers of rasterization and blending units. This means it's quite easy to put together a workload where more than half of the GPU is completely idle. Making the entire pipeline completely software-driven puts control of these decisions in the hands of developers.
Performance aside, having a software rasterization pipeline means the flexibility to set up whatever is desired. I've wanted fully programmable blending for 5 years. Now I can have it! Sending data back and forth across the bus taking too long? Process it all on the GPU! All of these things may be possible on current hardware using GPGPU programming techniques, but this is the first hardware that's designed for generality FIRST. That makes it a pretty big deal on its own, even if it's not the fastest chip on the block. "
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