Subject: Re: PDT-11?? can anyone tell me what this is?
To: None <>
From: John Wilson <>
List: port-vax
Date: 12/06/2001 22:55:28
>From: Stephen Bell <>

>I've just come across a PDT-11 (model: PDT-11150 CJ)
>It has 2 8" floppy drives, (which someone has labelled sy0: & dk0:)
>on the back there are 6 db25's labeled console,printer,modem, term 1, term 2 
>, term 3 
>What is this machine?? Can I make it run as a PDP11..
>It's nice 'n' small & looks like it would be quieter than
>my 11/44.

Quieter and vastly slower, but yeah it's a PDP-11, sort of -- LSI-11 chipset
with an internal bus (no Q-bus slots), and a couple of 8085s which emulate
the basic vital devices.  Those DB25s generally act like regular DL11 ports,
with the notable exception that the 8085 requires the terminal to set DTR
before I/O will be allowed (possible exception is the modem port, I forget),
so you can't quite get by with a data-leads-only serial cable.

The KW11L-style clock is normal, the DL11 programming interface is normal,
and the RXT11 floppy controller looks *real close* to an RX11/RXV11 to
software, but with enough details changed that RT-11 uses a totally
separate driver (PD.SYS instead of DX.SYS).  It's supported by RT-11 V4.0.
I wrote a four-user FORTH-79 system for it eons ago but there isn't much
space for each user (the machine has only 60 KB).

Note:  the console line auto-bauds when you start it up, so initially the
system is waiting for you to press "@" twice.  If it can't figure out what's
going on it starts anyway with some default setup, probably 9600/N/8/1 but
I could be wrong (I remember being happier with 4800 baud, KED tends to
glitch otherwise).  This depends on the three-way toggle switch on the back,
you can switch it to uODT instead of trying to boot off of the (top) 8" drive.

John Wilson
D Bit