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

Appendix: Introducing Intel® Graphics Performance Analyzers (Intel® GPA)
1.1.1.3 Memory Bandwidth
Evaluation within the memory bandwidth domain is a less precise science. With
current technologies, sustained bandwidth is roughly 65-75% of the computed peak
bandwidth, meaning that there is a significant portion of bandwidth that is likely
consumed by the CPU and not available as a resource to a bandwidth hungry
application such as a game even if no other high-bandwidth applications are running
on the CPU.
A good general rule is that if the time averaged bandwidth value is in the vicinity of
70%, the application may be bandwidth limited. If a bandwidth bounded situation is
suspected, the following checks may help confirm it:
Monitor the memory bandwidth usage with Intel® GPA. From this, you should be
able to get a reasonable estimate of the bandwidth the application is using. Note
that the Intel® GPA tool shows the overall usage and not just that used by the title
application, so this will be a rough estimate in terms of analyzing a single game
application, but it provides some data to start with. If the bandwidth as shown in
Intel® GPA‟s System Analyzer while the game is running is utilizing 90%+, the
game is likely bandwidth limited.
Recall from the Intel® HD Graphics architecture diagram that the GPU uses system
memory. Add in more main memory to the system or if the system is maxed out,
take some out and see if the frame rate varies significantly. A significant
performance change indicates a memory limitation.
How to maximize graphics performance on Intel® Integrated Graphics 43