3 ms·

I have absolutely no idea about the processor in the Pi 2, but I got all the specs for the Pi 1 from here: https://github.com/hermanhermitage/videocoreiv https

I have absolutely no idea about the processor in the Pi 2, but I got all the specs for the Pi 1 from here: https://github.com/hermanhermitage/videocoreiv https://github.com/hermanhermitage/videocoreiv (It's a beautiful processor. 32 registers, built in DSP, built in vector processing, some really elegant instruction design, dual core, and enough weirdness that writing good code is satisfying without being frustrating. No double precision float, alas, although it's got single precision, and for some bizarre reason there's no adc or sbc instruction which makes 64 bit arithmetic annoying.) If you're interested in playing with it, you might also like a look at my half-finished pure-VC4-code boot loader here: https://cowlark.com/piface https://cowlark.com/piface Stick it on an SD card, hook up a serial terminal, and it'll boot directly on the VC4 without even starting up the ARM.

voltagex_ 12y ago
Whoa, does that mean there's a chance of replacing the proprietary bootloader on the Pi? It's the most common complaint I see here.
- david-given 12y ago
  You can replace the proprietary bootloader on the SD card. You can't replace the one in the ROM. And while running executables is easy --- just drop a VC4 binary called bootcode.bin onto the root directory of the card and the ROM loader will load and run it --- there's a lot of hardware setup which still needs to be figured out; such as initialising the SDRAM. I originally wanted to get Prex (a Minix-like microkernel OS with a Unix interface which doesn't need an MMU) running on the VC4, but I need an actual working compiler for that.
  - acqq 12y ago
    May I ask you: why programming VC4 (apart from taking over the control of the rest of Raspberry Pi?) It's only 250 MHz? And if you want the new control of the Raspberry Pi, why, as it's so proprietary?
    - david-given 12y ago
      Because the VC4 is really cool, basically.
    - nitrogen 12y ago
      Clock speed is only a very small part of the performance of a chip when comparing across completely different architectures (like VC4 vs. ARM).
phire 12y ago
Pi 2 apparently has the exact same GPU/VPU as the Pi 1. The only thing they changed was the arm cores and the memory subsystem.

voltagex_ 12y ago

Whoa, does that mean there's a chance of replacing the proprietary bootloader on the Pi? It's the most common complaint I see here.

david-given 12y ago
You can replace the proprietary bootloader on the SD card. You can't replace the one in the ROM. And while running executables is easy --- just drop a VC4 binary called bootcode.bin onto the root directory of the card and the ROM loader will load and run it --- there's a lot of hardware setup which still needs to be figured out; such as initialising the SDRAM. I originally wanted to get Prex (a Minix-like microkernel OS with a Unix interface which doesn't need an MMU) running on the VC4, but I need an actual working compiler for that.
- acqq 12y ago
  May I ask you: why programming VC4 (apart from taking over the control of the rest of Raspberry Pi?) It's only 250 MHz? And if you want the new control of the Raspberry Pi, why, as it's so proprietary?
  - david-given 12y ago
    Because the VC4 is really cool, basically.
  - nitrogen 12y ago
    Clock speed is only a very small part of the performance of a chip when comparing across completely different architectures (like VC4 vs. ARM).

phire 12y ago

Pi 2 apparently has the exact same GPU/VPU as the Pi 1. The only thing they changed was the arm cores and the memory subsystem.