Which PDP?

[Ashley Carder]

> For 1970s PDPs, the easiest to aquire would be something in a PDP-11
> or PDP-8.  Since you want a unix-like OS with a C compiler, that
> pretty much pushes out the -8.
> 
> > The 11/34 looks a good choice at this stage?
> 
> 11/34s are among the cheapest PDP-11s from the 1970s (presuming you
> don't get a haul-it-away deal).  The CPU, memory, and some peripherals
> fits in one BA-11 cabinet (10.5" tall, 19" wide, rack depth), but one
> can add a second BA-11 if one really needs more than 3 backplanes. 
> The max memory is 256K (18-bit addressing), which is enough for
> something like a v7 or a XINU, but would be a bit cramped for 2.9BSD.
> 
> Disks are probably going to be your biggest problem... the RK05 was a
> common disk in the 11/34 era, at 2.5MB per drive (4 drives per
> controller).  v7 might fit, but 2.9BSD will be _really_ cramped. 
> RL02s may be easier to locate, but they are 1980s tech essentially,
> and even at 10MB, are a bit on the small side for UNIXy work (but are
> great for RT-11, etc.)
> 
> I never did solve my Unibus disk issue for non-MSCP disks... UDA50s
> are not impossible to find, but the disks tend towards the heavy side
> compared to, say, ESDI disks.  It matters less to me than it used to,
> since it's possible now to use MSCP disks with 2.9BSD (formerly, one
> had to go to 2.11, and that required a split I&D machine, of which I
> have few).
> 
> If an 11/23 is not too new (it might be 1979), it's a nice choice
> because a) it's 22-bit (except for rev A boards)allowing up to 4Mb of
> RAM, b) it _is_ compact, c) it's expensive, but a Qbus SCSI card is
> easier to find than a Unibus SCSI card.  They are also somewhat common
> (I got my first one in 1986 for a whopping $300, then used that to do
> work on a contact that was my bread and butter for two years)
> 
> An 11/23 w/RLV11 (requires CD-capable backplane) or RLV21 and a couple
> of RL02s is a nice PDP-11 system, and fits in a 42" tall rack.  Not
> sure you could get all of that for under a grand these days, but it's
> a place to start.

I also have a nice working 11/23 that I'm thinking about selling.  I can 
put it in a short rack with an RL02 drive. It already has the controller
for the RL01/RL02 drives, as well as the RX02 controller.  It has a
multiplexer, so you could run multiple terminals if you wanted to.
I can also configure the 11/34A with a DZ11 multiplexer, if you want to
run multiple terminals on a unibus machine.  

If you (or anyone else) is interested in either the 11/34A or the 11/23, 
contact me off-list. 

Thanks,
Ashley
wacarder at usit.net