http://bugs.winehq.org/show_bug.cgi?id=35112
--- Comment #4 from Stefan Dösinger stefan@codeweavers.com --- I think the value you're looking at is MaxPrimitiveCount. My Evergreen-class AMD GPU sets MaxPrimitiveCount = 0x555555 and MaxVertexIndex = 0xffffff.
MaxStreamStride on Windows is 508, MaxStreams 16 (no surprise there, that's an SDK define).
I'll send a patch to raise MaxPrimitiveCount.