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There are certain recurrent trivia when it comes to memory performance. One of them is the fact that integrated graphics will draw bandwith and, thus, cause system performance to sag. This is all nice and dandy but without specifying the exact resolution and color depth as well as the refresh rate of the monitor, the benchmarks are completely useless since the amount of memory bandwidth drawn by the the integrated graphics are a direct function of the three aforementioned parameters.

A simple formula to describe the math behind this phenomenon is that the graphics memory bandwidh = pixel resolution x color depth x vertical refresh rate of the monitor. For example, at 800 x 600 x 32 bpp (or 16 bpp) and a 60 Hz refresh rate, the raw memory bandwidth consumed by the integrated graphics will be:

• 800 x 600 x (32/8)* x 60 = 115.2 MB/sec (* 32bit color =4 Bytes, therefore 32/8)
• 800 x 600 x (16/8)* x 60 = 57.6 MB/sec (* 16bit color =2 Bytes, therefore 16/8)

Benchmark Results

Memory bandwidth measured by Sandra2003 at different resolutions and color depth of the integrated graphics compared to the raw system memory bandwidth when using an external AGP card. 8x6: 800x600; 10x7: 1024x768; 12x10: 1280x1024; 16x12: 1600x1200

Let's look at the numbers from a few different perspectives:

• How much of a performance hit is associated with every resolution?
• How closely matches the performance hit the predicted theoretical value?

Performance hit (in percent) of the memory subsystem depending on the different resolutions and color depth settings (at constant 60 MHz VSync). What we all already knew from graphics cards is that 32 bit color is a memory bandwidth hog compared to 16 bit. Therefore, for office applications, if there is really a need for performance, it may be better to short-term reduce the color depth to 16 bit.

We mentioned it above, the performance hit is much greater than the theoretical predictions. We simply took the Integer Bandwidth and subtracted the theoretical bandwidth for each resolution for the blue bars whereas the red bars show the real measurements. This is as far as we will go here, the keyword is latencies and will be addressed in a separate article in depth.

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