Very bad performance Tegra 4 (MC Mojo)

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It's also important that the Tegra 4 is just a different GPU. Most likely your performance is mainly restricted by your graphics speed, not your CPU Mhz.

The Rockchip had:
Mali-400 MP4 GPU, up to 600 MHz (typically 533 MHz)

The Tegra 4 has:
VLIW based, 672 MHz

That being said, Mali-400 is really not high on the list of recommended GPUs for PPSSPP, I would expect Tegra 4 to outperform it. I think the things pointed out by TkSilver and LunaMoo are likely the key reasons.

The slowest things that have been added recently are generally all bucketed into two different settings:

Simulate block transfer [X] - checked by default
Disable slow buffer effects [ ] - not checked by default

To have better speed, but graphical effect issues (which are the same ones from a year or two ago), swap those checkboxes - uncheck block transfer, and check the option to disable slower effects.

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