RX50 on RQDX3 on 2.11BSD

Jason T. Miller jasomill at shaffstall.com
Thu Jun 8 03:15:53 AEST 2000

> 	Wow, quite a bit of interest in 2.11 these days - I suppose I should
> 	get back into it (too many other projects, etc and so little time ;))
It's the first PDP operating system I've enjoyed working with, and one of
the coolest UNIX implementations I've had the pleasure of working with.
Every programmer who writes 150MB bloatware should study it.

> 	Not for eons - the RX50 I had was so flakey (well, actually it finally
> 	got to the point it was declared broke) it was replaced with a 1.2mb
> 	5.25" Teac "PC" drive).
I unearthed two Teac 55-G series floppy drives, and they're both broken
(won't format w/verify) -- the RX50 isn't the only flakey floppy. I've got
a few Toshibas and Matsushitas I'm gonna fool around with, though. Though
I find that about 90% of what I learn about everything computer related
involves one thing or another that doesn't work; so in a way I can thank
DEC for screwball H/W. About 10 YA, I used a DECmate II with an RX50 on a
daily basis, and had 0 problems; of course, I had preformatted DEC disks
and no interchange (at the time I had two computers -- an Atari 130XE and
DECmate II)

> 	Using 'cmp -l' will show where the differences are.   If they are only
> 	in the first couple sectors but the rest compare ok then I think I
> 	know what the problem might be.

Some is, some ain't. Aside from the also-mentioned "interleave problem,"
whereby the RX50 seems to interleave output data (isn't the hardware
supposed to take care of this, if it is indeed hardware interleave, 
though I'm 95% sure I formatted 1:1...yes, unless the RQDX3 is unlike
_every_ floppy controller I've seen in the past ten years)

> 	I do not know why the first two sectors are not being written if the
> 	synthetic label is being used.  It's probably a bug having to deal
> 	with not setting the "enable write for label area" when the fake label
> 	is being used.  Sigh.   I have a floppy drive on my 11/73 - I'll try
> 	to find time and play around before going on vacation in a couple weeks.

I, also, although I'm not going on vacation in the near future, and I
don't have an 11/73 -- but, I suppose if I can find time to play with my
PDP @ all (which I suppose I have -- it's now, courtesy of Network Address
Translation and SLIP, not only connected to my Apartment Network, but also
to the Internet. Now to find a Web browser that fits in 64K I space or
segments well. Is CERN line-mode still being maintaned?), I'll work on
this. I hope to be able to use the RX50 for sneakernet purposes, despite
my network connection, as 19.2K is pretty damned slow, and while I'm
excited at the prospect of diviplexing SLIP over all 40 ports on all five
of my muxes, I'm somewhat less excited at the prospect of designing and
coding it; besides, I only have three serial ports on my PC, and one's for
the modem). Though Priority One is getting my LA75 working -- once again
It Worked In RSX (much better than I did, I might add :).

> 	Try doing a 
> 		disklabel -W /dev/rra12a
> 	Oh, for debugging purposes you can enable more or all of the MSCP
> 	messages with the 'sysctl' command:
> 		sysctl -w machdep.mscp.printf=X

I will. Thanks. I didn't even know 2.11 had 'sysctl'. Cool.


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