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Carveout memory (Linux)

 
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On the Tegra modules, the CPU shares the memory with the graphic core (see http://en.wikipedia.org/wiki/Shared_graphics_memory ). The Tegra T20 needs this amount to be fixed and specified at boot-time, this memory is called carveout by NVIDIA.
Usually Linux reports substantially less RAM than the module specification states (e.g. 126MB on a Colibri T20 256MB). Carveout, the framebuffers and memory used inside the Kernel (around 25MB) add up to the difference to the total RAM size.

Configure carveout memory

One can adjust it from within U-Boot as follows:

setenv memargs 'mem=218M@0M fbmem=6M@218M nvmem=32M@224M'
save

This change results in around 190MB available RAM for user space applications.

Note: Graphics/multimedia performance might be severely crippled should you lower it much from its default values.