| What | Removed | Added |
|---|---|---|
| Resolution | NOTABUG | FIXED |
Comment # 4
on bug 105256
from Roland Scheidegger
(In reply to Logan McNaughton from comment #2) > Interesting, is this documented somewhere? How do you know what data formats > the HW supports? Is there any other hardware besides these cards that don't > support it? > > I'll have the users test using GL_UNSIGNED_SHORT I'm not sure if AMD (or ATI) had some perf guides published where this was stated. You can, however, see this from the published register guides - https://developer.amd.com/resources/developer-guides-manuals/ It says VGT_INDEX_16 and VGT_INDEX_32 as valid values for VGT_DMA_INDEX_TYPE (for evergreen, others should be similar), interestingly however it's already a 2-bit value there. (Actually the register guides only seem to go up to Sea Islands, so you can't even see that it is supported starting with VI.) A look at the mesa driver is probably easier though :-). This should affect all amd/ati hw up to Sea Islands. Of course, if you use old-school non-vbo element data, it's probably no big deal. At a very quick glance at the driver code, it looks like newer nvidia chips can handle it (everything from g80). nv30/nv40 cannot, but there it looks like nv30 will emulate index buffers anyway, so the only chips which this might make a difference is nv40 family. Looks like all intel chips can handle it fine. That said, even if the slowdown is due to this, I'm not convinced the driver couldn't do better (though it does not look trivial to do better). But it's one of the features which noone really expects to get used, therefore it's good enough as long as it works correctly... You can't query this afaik and just have to know... Apparently using GL_UNSIGNED_BYTE indices was simply broken at some point with windows drivers too - it's possible the blob implements a more sophisticated emulation strategy: https://community.amd.com/thread/159040
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