> On 24 Jun, 2016, at 03:02, Juliusz Chroboczek
> <j...@pps.univ-paris-diderot.fr> wrote:
>
> Raspberry Pi: doesn't run armhf userspace, no wifi, eth connected by USB;
> Raspberry Pi v2/v3: requires binary blobs, wifi and eth connected over USB;
Actually, the only substantial difference between the first R-Pi and the second
is one ARM1176JZF-S core (ARMv6 with an FPU) versus four Cortex-A7s (ARMv7-A
with FPU and SIMD).
They can both run armhf userspace, as we were just discussing, and they can
both have external wifi attached via USB. What the first version *can’t* do is
run ARMv7 code - which isn’t very much of a difference, honestly. There is a
big performance jump though.
The third, current version gets four Cortex-A53s (which support AArch64 as well
as 32-bit code) and includes a built-in wifi radio attached via SDIO.
Otherwise, it’s identical to the second version. I haven’t got one of these
yet. I’m told that all the official R-Pi distros remain 32-bit for
compatibility with the older versions, but that’s not a concern if you’re
rolling your own.
They also *all* require a binary blob to bootstrap the chip. Apparently
Broadcom’s SoC architecture puts the GPU - which occupies the lion’s share of
the die area - in charge of boot, with the CPU subordinate. In fact the
original R-Pi’s chip was designed as an independent embedded-class GPU, with
its ARM core provided as a mere command translator! Needless to say, the GPU
hardware goes woefully underutilised, but is retained in the newer versions to
preserve compatibility.
I agree however that none of the R-Pis make good routers at the performance
levels we want. They just don’t have the right kind of I/O: we need direct or
PCIe attachment of Ethernet and wifi MACs, not USB and SDIO.
- Jonathan Morton
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