3 Jan
2014
3 Jan
'14
2:09 p.m.
On Fri, Jan 3, 2014 at 4:17 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
I'm just getting started in DEC stuff in general
and RL02 drives in particular. I'm
putting together a PDP-11/44 system, and I hope to try running both RT11 and
BSD on it.
The 11/44 has split I&D so you can go with 2.9BSD or 2.11BSD.
Generally speaking,
you'd probably want to go with 2.11BSD because you can.
Would a two-drive system be sufficient, or would I
need more storage space?
I have four RL02 drives in unknown condition, but I was only planning to rack
up two of them with the PDP-11/44 and a Kennedy 9610 9-track tape drive.
My experience is that I was able to fit the base install on the first RL02 pack,
but there wasn't room to pull the sources and rebuild the kernel without more
storage. Even so, 20MB total was kinda tight, maybe too tight. Back when
this hardware was current, it was IIRC easy to plunk 2BSD onto one or two
RK07s (28MB each). When I started playing with simh 15+ years ago, it was
easier to define an RP03 and install into one big 60MB pot (which is how I
helped find a simh bug long ago). You can give it a try now with simh by
practicing with a couple of 10MB image files and the 2BSD distro tape images.
It's an authentic experience in terms of the approach you'd have to take
and the commands you'd have to type (without bad blocks and tape errors
to pull you astray). If it fits on 2x RL02 in simh, it'll be the same on real
hardware. That reminds me - you have to have error-free packs. DEC used
to sell RL02-EF packs for use with UNIX (RT-11 can mark bad spots
on the disk and if they aren't in the first tracks or if there aren't too many,
you can mark those sectors allocated and work around them. Not so with
BSD).
For RT-11, even a single RL02 is plenty of space. I used develop applications
on an 11/23 and an RL01 was enough for the OS and all my code.
My PDP-11/44 pile came with an RL11 board and the
cable from it to the
first RL02 drive. It doesn't have a bulkhead fitting; it just goes from
the controller directly to the connector that plugs into the back of an
RL02 drive. I haven't looked at the cable carefully yet, but I can
examine, measure and photograph it if that would be helpful to anybody
else in this thread.
The bulkhead bracket was convenient but not essential. To get out of the
CPU cabinet, you almost certainly have a flat 40-pin cable, then the
transition connector, then probably the usual drive-to-drive round cable,
but just laying in a line, not bolted to your rack. It will work just fine but
there's a risk of kinking or pinching cables if you move the drives around
a lot (the bracket has a spot to screw down a tab on the shield of the
round cable as a strain relief with either a 6-32 or 4-40 machine screw).
I know I have at least 1-2 bad cables from excessive flex/pinching (I've
thought about cutting them at the point of physical damage and trying
to make one or two of them into a BC80M cable since I have the right
crimper for those Berg pins).
BTW, I am looking for drive ID lenses for my RL02
drives. I need a "1" and
a "2", and I could either buy them outright or trade "0" lenses for
them. My
RL02 pile came with three "0" lenses and a "3".
My recollection is that it was common to have 1-2 drives, but not 3-4 (for
reasons of cost), and as systems were consolidated, there were more "0"
plugs than the others combined.
I've thought about molding replacements or even 3D printing them (they'd
be suitably light-transmissive if made from natural ABS or especially natural
or clear PLA) but I haven't tried making an STL of them. There'd be a risk
of the fingers snapping off and getting stuck in the switch mechanism, but
I think an ABS drive plug that was subjected to the acetone vapor treatment
would firm up nicely and be resistant to the layers separating.
Anyone care to make up an engineering drawing of the plug with tolerances
in the 0.1mm range?
-ethan