Intel HD Graphics DirectX Developer's Guide (Sandy Bridge)

Intel® HD Graphics DirectX* Developer's Guide
3.10.6 Avoid writing to unlocked buffers
We have found multiple cases of corruption which were caused by the writes to
unlocked buffers. Typically the title first locked the buffer, then unlocked the buffer
and then attempted to writing to the buffer that is already unlocked. This sometimes
works because the system might have not moved the buffer and has not dispatched
the rendering commands to the graphics hardware. This is inconsistent with Microsoft
DirectX* specifications and is not safe for applications to expect it to work
consistently.
Avoid writing to buffers that have not been locked. Some drivers on other hardware
platforms are more forgiving of this approach, and may handle it gracefully. The Intel
driver makes optimizations based on the specified behavior of the API, so the behavior
of this platform will be undefined in this case.
3.10.7 Avoid tight polling on queries
Tight polling on event/occlusion queries degrade performance by interfering with the
GPU‟s turbo mode operation.
Allow for queries to work asynchronously and avoid waiting on the query response
immediately after sending the query.
34 Document Number: 321371-002US