Dennis Lee Bieber  wrote:
> 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.

And I thought this was already getting confusing just with the ARM version
numbers. So to summarise: V.6 may have many (but not all) of the features
of V.7 as extended features. The Debian armel builds do not use the
floating point features of the ARM V.6 CPUs used in the PRI1/0. The armhf
builds do, but also enable some of the ARM V.7 features not available for
ARM V.6, so they might crash sometimes.

>        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
>
>

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