[SunRescue] NetBSD 1.4 miniroot problem fixed

[BSD Bob]

> ..... How have you got yours ID'd
> >and set up?  Is it a live bootable system, or just a miniroot on swap?
>  
>    Actually, I have several different miniroots on it, and a filesystem
> which contains all the install sets for sun3 and sparc.

If you are interested in a snapshot from a couple of days ago, I just
put a snapshot build from one on the list that did not have room for
it on his machine, on 152.1.207.52/pub/NetBSD/19991110-sun3.tar.
If you can, please try it out.  I will run off a tapeset tonight and
give it a whirl on the old 3/260 crate and 3/110 crate.

Any feedback would be appreciated.

> >This was what I was wondering about the clock speed for the CPU.
> >The sun3's run at 12/16/25(?) mhz, and the 4/260's are at around
> >25/30 somethihng?
> 
>    3/50		15.7MHz or thereabouts
>    3/75,3/1xx	16.67MHz
>    3/60,3/80	20MHz
>    3/2xx	25MHz
>    3/4xx	33MHz
> 
>    4/2xx	16.67MHz (!)

The 4/260 runs the sparc a 16.67 mhz!  Yikes, that is slow.
It should not need any extra clocking then, if it is that slow.
Mebbie that points to some other scsi problem thing.

> >What if you half clock the cpu?   Will that
> >allow enough time for the scsi to settle?  If that is the case,
> >does the code need a wait loop for a couple of instructions to
> >allow the scsi to catch up with the cpu?  Nothing fancy, but just
> >a millisecond or two. 
> 
>    Don't know. To be honest, I've never had very good luck with Sun-3
> SCSI controllers, even under SunOS. I'd replaced them all with Sun-2
> units, which might not have been quite as fast but actually worked
> reliably. I wish somebody would write a driver for them.

Someone had a skeleton sun2 scsi driver at one point in time.
I dunno where the code vaporized to.  I had to do a lot of odd
begging to scrounge up a couple of sun3 controllers for mine.
Then I combined the sun2/sun3 parts and made the combined I/O
versions.  The seem to work fine on SunOS.  Sometimes on NetBSD.

.....

I have never run zips on my machines, so have not run into zip drive
funzies, yet.  I don't trust the reliability of the media.  Folks around
here tend to swear at them more often than not on Gatesware machines.

>    My current problem with the 3/4xx is "ie0: DMA underrun" messages,
> which occur very occasionally when transferring enormous files via FTP.
> So far, these seem to simply be annoyances; the data appears to be
> intact.

I ran into that a few times, but also no real problem.

> >I can never seem to get two of the DB50 cables on-line in series on
> >the scsi bus.  One is fine, but the second one blows up.
> 
>    I once got three in a row working -- three shoeboxes hanging off a
> 3/60. That was the system that wouldn't work if it was terminated, and
> it insisted that the first two cables had to be short and the last one
> long. Any other arrangement, including making all three cables short
> ones, was error city.

I will have to check that out.  I have two of the short cables and one
of the long cables.  The magick has to do with radio frequency reflections
on the cables, as I understand it.  Thus the length of 6 meters is a
critical length where such things as impedance transformations and
rounding of square waves begins to occur which give rise to data errors.
Your concoction of cables and lengths may be such as to give an artificial
correction to the problem by making the line appear resonant.  I expect
the hardware in the sun controllers was marginal anyway for that era.
Anyone tried putting everything in one external box with one short cable
and short internal cabling and seeing of that corrects such scsi funzies?

>    Random rant: why is it that mass storage busses all have so many
> problems? MFM, RLL, and ESDI worked pretty darn well but the two-disk
> limit was a bummer. SCSI allows for plenty of expansion, but it's pretty
> much plug-and-pray. IDE is still limited to two drives and has problems
> with devices that don't get along, although these days with twin
> controllers the norm you can usually separate devices, and when you can
> get a 40-gigabyte disk for less than $300 it doesn't matter so much if
> you can't have very many.
>    But why hasn't anybody come up with anything better?

I think scsi is OK, it is just the cabling length problem that most often
gets me.  If I remake cabling as short as possible (like inside my VAX)
it can hang all sorts of things with no problem.  IFF the external run
gets beyond another 5 feet or so, then the whole thing takes a dive.
The cabling in the old Sun deskside VME crates from the sun3 era are
way too long.  I was thinking of making up a short ribbon cable that
would go directly up through the top of the cardcage into the top drive
bay, and not go up and around via the backplane passthrough.  I  am
expecting I could cut the cable length in half that way, and still put
4 drives and tape up in that top bay.  That kind of approach may be
the optimal solution.  It would require opening up a 1/2 inch by 3 inch
slot in the top bay drive plate and then carefully mounting all the
devices on fresh brackets to keep the cable run as short as possible.
I may try that over the holidays if I can squeeze a little time.

There has gotta be some way to optimize these old crates.

Bob