[libre-riscv-dev] System-Wide Complexity Rant (was store computation unit)

Samuel Falvo II sam.falvo at gmail.com
Wed Jun 5 06:25:35 BST 2019

On Tue, Jun 4, 2019 at 10:01 PM Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> design and production* that DTB support is just a complete waste of time,
> the lesson that I learned is that expecting compatibility is just not
> realistic.

I concur, which is why I ranted a bit.  I don't believe it *has* to be this way.

> Intel interoperability is only realistic because actually (A) the
> differences are hidden behind the BIOS (ACPI notwithstanding, no please
> don't rant about it, we haven't got time), B almost all peripherals now
> connected to x86 systems are either USB or they are PCIe.

PCIe has its autoconfig features inspired by Amiga Autoconfig; so by
illustrating A and B above, you kind of supported my vision.  The next
steps in the chain of thinking, then, are:

1) making sure the processor has a sane development path going forward.
2) breaking the reliance upon special interest groups backing I/O
interfaces.  In other words, we need not only open ISAs and libre CPUs
that implement them, but libre I/O interconnects as well.

> Only coreboot and uboot developers *actually* need to know about the fact
> that there exists a Quad SPI NOR Flash IC from which they can chain load
> the firmware.

Fun fact: my current Kestrel-3 hardware hard-codes this knowledge in
hardware.  The system firmware has _zero_ knowledge of how the
firmware is actually stored.  The ROMA core hides that in _hardware_.
The only thing the software takes responsibility for is copying itself
into RAM since it knows that'll be the fastest way to run; but it's
important to note that it's not required to operate.

Getting to the point of configuring SDRAM chips will pose an
interesting design challenge, but I'll cross that bridge when I get
there.  For now, I'm quite happy using nothing but static RAM.

> Try to fix all of these issues at once and I guarantee that you will either
> go mad or you will be grey or wrinkly long before you should be grey *and*
> wrinkly.

To be fair, I'm not asking for a perfect solution up-front.  I'm
asking for awareness, and seeking to reverse the trend in people's
thinking that complexity is inexorable.  I firmly believe that it's
not.  Amiga proved this in 1984.  It took the PC industry 15 years to
finally get their act together and compete on the Amiga's level, but
to do so, it involved /massive/ amounts of complexity in the process.

> Stay sane, my friend... :)

Too many people think what I'm doing counts as clinical insanity
already.  I'm a lost cause.  ;P

Samuel A. Falvo II

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