Re: PSA: Clock drift and pkgin

[Johnny Billquist <bqt%softjar.se@localhost>]

On 2023-12-20 17:13, Maciej W. Rozycki wrote:
> On Tue, 19 Dec 2023, Johnny Billquist wrote:
>
> > >    The DS1287 is an example source of the timer interrupt with some systems
> > > where a high-resolution timer has to provided separately, just as with the
> > > 4000/60.  By no means I find the DS1287 itself a high-resolution timer.
> >
> > Ok. Then we agree, and I'll drop that. :)
> >
> > I would still think that if you have the full ICCS and ICR register in the
> > VAX, it is better than such a chip, or probably any chip.
>
>   Full ICCS/ICR isn't necessarily better than a having a truly free-running
> counter of a suitable width available, such as with the KA60, because such
> a counter is immune to missed timer interrupts.

Fair enough. You still want to have some regular interrupt, and you want 
to have a high precision time indication. ICCS/ICR will give both for 
you, down to microsecond resolution. And with interrupts at 10ms, it 
should not be a case of lost interrupts, really.

A counter will sooner or later overflow, and you need some way of 
dealing with that, so it's not an inherently solved problem just because 
you have that hardware. You then need some way of, from time to time, 
note the time to be able to deal with the overflows.

But sure, it might be a bit more relaxed in the timeliness of the 
processing.

> > >    I do have a 4000/90 too, but it suffers from an issue I yet need to debug
> > > where it ever boots NetBSD 9 from local storage only once.  Then the OS
> > > corrupts itself somehow in storage such that any subsequent attempt to
> > > boot causes the firmware to fail:
> >
> > Weird. I have a 4000/90, and have never observed such issues. But now it's a
> > few months since I last spun it up. I plan to test it out with the current
> > updates after christmas.
>
>   I don't know what could be causing it.  I made the installation with my
> 4000/60 using the NetBSD installer while at my lab where it was more
> convenient to me and I had time available to experiment (it was during a
> COVID-19 pandemic lockdown), dd'ed the resulting disk contents to another,
> identical disk (and thankfully to a backup file too) and placed the latter
> disk in my 4000/90 which I keep at a different site across Europe.

It's just confusingly weird.

>   Maybe it is not the canonical way to install the OS, but I can see no
> reason for this to fail as the KA90 mainboard is a drop-in upgrade for the
> KA60, so the console ABI of both is the same.  Besides, it does boot once,
> so it's not that there is an issue with the pristine installation itself
> being incompatible with the 4000/90, but rather the OS writing something
> to storage while running that corrupts the bootloader or suchlike.
>
>   Besides, there is an issue with netbooting my 4000/90, i.e. the NetBSD
> bootloader loads, but then fails to proceed, so I couldn't have installed
> the system the proper way anyway:

The bootloader have been broken for many years. I've been keeping a 
rather old version around, since whenever I've done an update, booting 
stopped working until I restored the old /boot again (which is a pain to 
do).

But it seems the boot I built new with the new fixed tools and so on, 
actually do work. Which is already a step forward. But I still want to 
check/confirm this on real hardware before I declare it a success.

  Johnny

--
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol