On a sunny day (Tue, 17 Mar 2020 11:16:38 +0100) it happened "A. Dumas"
 wrote in :

>On 17/03/2020 08:18, Jan Panteltje wrote:
>> Not so sure about that, once tried the latest download
>> and tried it in my old PI, and it did not even boot.
>> Checksum was OK, no download error.
>
>Something else was wrong. The old full-size SD card slots were wonky,
>maybe that failed? All downloads of the RPi Foundation work with all
>RPis. That's precisely the reason why they stayed on 32-bit.

Possible, but bit unlikely, been using those SDcards without problems for
years.
And, even if it booted, then it still would not work for some
software due to the GPIO addressing, example:
 http://panteltje.com/panteltje/newsflex/download.html#freq_pi


I usually get a recent release, like that Buster for my P4,
and from that point onwards modify it, never 'upgrade'.
If I ever buy a Pi5 ?? same procedure ;-)

What would a Pi5 be able to do? Interesting question.

Maybe it is my hardware background,
I see the software and hardware as one thing,
raspberry is not just an operating system (Linux)[1] but a huge wilderness of
applications.
Expecting to - or making it to run on all models would be a very limiting
requirement.

But maybe you are right, maybe it detects the processor on boot up,
but this is my experience.

[1] the function of an operating system is to as much as possible make an
interface to the hardware that allows the same programs to run on as  many
types of hardware.
For programs that by-pass that OS and use user space access to the hardware
it would be a tall order to make those run on every model (they don't), needs a
rewrite if at all possible.

So much for the basics part :-)

My advice is keep it simple, too much spaghetti in all those releases.

As to 32 bits... mm you know, programming in asm on a Microchip PIC,
setting and testing a flag
 btfss   spi_byte, 7
...
 bsf             SPI_SCK

takes ONE bit of ONE byte.

Now even in C I see this:
int too_hot;
int alarm_flag;
if(too_hot) alarm_flag = 1;

On an int that takes 64 bit system this takes 8 bytes!
Basically 8 * 8 = 64 x less efficient.
Not even mentioning the memory access delay.. alignment.
Just FYI.

LOL
And I wonder, Yes I wonder, Why

But bloat sells.
And memory per byte gets cheaper all the time

Just something to think about...

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