Re: Raspberry Pi
On Sunday 01 March 2020 13:31:21 Pete Batard wrote:
> On 2020.03.01 16:30, Gene Heskett wrote:
> >> Debian 10.3 ARM64 should install and work just fine on the Pi 3,
> >> including full graphical mode. No need for 32-bit.
> >
> > Yes, I've done it, works fine, with one glaring exception all the 64
> > bit fans refuse to recognize.
>
> I think you're assuming a bit too much with that statement with the
> idea that the world is populated by close-minded 64-bit ARM "fans".
>
> I don't have a particular bone with either. OP mentioned that they had
> been trying to install "debian-10.3.0-arm64-xfce-CD-1.iso", then
> someone replied that they should got with ARM 32 and raspbian instead,
> and all I said is that it wasn't necessary when you can get
> debian-10.3.0-arm64-xfce-CD-1.iso installed on a Pi 3 without too much
> trouble.
>
> So this is not exactly a "You *should* use 64-bit" matter. I just
> stated that OP could install the distro they were originally planning
> to install, and pointed to guides that explain how they should proceed
> to do so.
>
> > When called upon to run machinery that demands microsecond responses
> > in order to run that machinery smoothly AND accurately, the
> > increased latency caused by the 64 bits much larger stack frame to
> > be stored, and pulled back into active service when an interrupt
> > from the machine is received, slowing the response to the interrupt
> > from 5 microseconds to 50 or more is not tolleratable. armhf is
> > much faster, and when doing software stepping, which when the step
> > timing has jitter in its timed pulses, very rapidly kills motor
> > torque with increases in the timeing jitter, with a 50 microsecond
> > jitter killing over 75% of a motors usable power.
>
> Yes. All archs and software implementations on top of specific archs
> have advantages and drawbacks. But it seems to me like you are trying
> to imply that 64-bit should be avoided altogether on account of the
> one scenario you exposed above, whereas, just like there exists
> scenarios where 32-bit has the edge over 64-bit, there also exist
> scenario where 32 vs 64-bit won't make much of a significant
> difference, which, in lack of further indication, we can probably
> assume is OP's planned use.
>
> OP expressed their interest to use 64-bit Debian and said nothing
> about running machinery with it, so I hope you can appreciate that an
> answer that aims at helping OP go with the original arch they said
> they wanted to install, but seemed to have trouble installing, is not
> exactly invalidated by the point you raise.
>
> In other words, the point you make is very valid and something 64-bit
> users might indeed want to be made aware of. But it would have been
> made better without preceding it with what seems to me a rather
> reductive opinion of folks who do think that, just like 32-bit, 64-bit
> has its place.
>
> Regards,
>
> /Pete
The whole point of my rant is that the instant folks find out that 64 bit
will run on whatever platform we are discusing, and armhf needs more
attention paid to details like addressing beyond 3 gigs, PAE IOW, 6
months later there are no armhf distros left. Then we who do carve
steel are back to haunting the used boards market for the few surviving
Intel D-525-MW motherboards left in the wild, hoping everything on the
one we're buying blind on fleabay, still works. And paying $30 more
than it sold for new for the privilege of taking that chance.
Debian has a nice 64 bit net install, works well and had power bump to
power bump uptime in both an rpi3b and an rpi4b. So I built a couple 64
bit realtime kernels. Realtime-preempt for these so called kernels was
so poor and latency so long that 3/4 ton of moving machinery ran out of
buffer to keep it moving and stopped for lack of data in the buffer,
latency's were well over an millisec at times. running out of data in
excess of a millisecond several times a foot. An armhf kernel has 10%
of the peak latency of an arm64 kernel and runs that same machine from
an rpi4b with zero such stutters, while running the cpu's in an rpi4b at
only 800 Mhz.
There are 2 huge advantages to the debian arm64 builds, 1; it boots from
grub, and that seems to get rid of the /boot/overlay directory that only
raspbian (that I know of) uses, and which ATM means you have to use the
raspbian supplied src to build an preempt-rt kernel that will actually
boot on a pi. That, and only the raspi supplied srcs know about the mali
video, giving us full screen glxgears at 60 fps since buster 10.2. That
mali video is not now nor from statements made by debian folks, will
never be available from debian so debian is doomed to 3 fps framebuffer
displays. Bottom line is that only raspbian can give us what we need.
But no mailing list, its all forum, and as far as I am concerned their
forums search engine, to be used to find what one goes there to find, is
hopelessly broken.
I'll do an Andy Capp and shaddup now.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
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