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A comment on LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU. Parent comment

Re:LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU by TD-Linux on Monday May 02, 2016 @02:32PM (#11614123)
Yup. Check out the VideoCore ISA:

http://www.broadcom.com/docs/support/videocore/VideoCoreIV-A...

Note that in this case, the author is writing the bootloader firmware so performance isn't a major concern, though.

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Re:LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU by christina_b on Monday May 02, 2016 @03:26PM (#11614682)
This isn't the same, the document in question relates to the QPU ISA. The VPU ISA hasn't been officially documented but there were many projects that involved reverse engineering it. The VC4 ISA is documented here:

https://github.com/hermanhermitage/videocoreiv

The VPU is basically a general purpose RISC processor with some fancy vector instructions on top. In fact, most of the firmware that runs on it is written in C.

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Re:LLVM Backend for the VideoCore4, Raspberry Pi 2 VPU by TD-Linux on Monday May 02, 2016 @04:01PM (#11615043)
Ah okay, this explains a lot! I somehow thought that the initial boot happened on the QPU.
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