On Thu, 9 May 2019 23:27:56 +0000 (UTC), not@telling.you.invalid (Computer
Nerd Kev) declaimed the following:

>I see, as I've been looking at Pi Zero stuff, I got the impression
>that they were all ARM V.6, but I guess it's just that a lot of the
>software is built to be compatible with ARM V.6 as a common minimum
>spec.
>
 ARM v6 actually is /newer/ than ARM v7.

 NO ARM core has built-in floating point -- it is an extension that can
be specified when designing a chip using ARM cores. You'd have to check the
data sheet for the chip to determine if the designer included the floating
point unit. Most v7 and v6 based chips tend to have the hardware floating
point.

http://single-boards.com/armv6-vs-armv7/
"""
    ARMv6 architecture
    Includes VFPv2 optionally (usually is implemented).

    ARMv7 architecture
    Includes VFPv3 optionally (usually is implemented). VFPv3 brings
several minor improvements. Mainly it adds a new capabilities to
instructions VCVT and VMOV. Some operations with floating point values can
run more efficiently because of the improvement.
"""
(VFP => Vector Floating Point)


 v6 has Thumb-1 -- the processor has to be switched between full
instruction set and compressed Thumb instruction set. v7 supports Thumb-2,
in which full 32-bit instructions and compressed 16-bit Thumb-2
instructions can be intermixed without an explicit mode change.

 v6 does not have the single-precision NEON SIMD engine. v7 may have
NEON, which could be useful for 2D/3D graphics processing.

 Buried in the bottom of that link appear the key phrase... At least for
Debian-provided releases it implies armhf /also uses Thumb-2/, which is not
available for v6 -- so needs the armel build. Though the Debian site
indicates that armhf also needs VFPv3.

 BUT -- if one compiles the OS for themselves, one might be able to
compile without Thumb instructions, but still using VFP -- that compile
would be usable on both v6 and v7 chips, and hence qualify as an armhf type
build.

 So the question becomes: what does "Raspbian" (via NOOBS) contain.
After all, the R-Pi foundation seems to release only a single OS installer
file, regardless of architecture (I'm still hoping they eventually split
off an optional 64-bit Raspbian).  I know for a fact (just ran it) that
apt-get is getting armhf files for my 3B


--
 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com

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