From: karttu@mits.mdata.fi (Antti Karttunen)
Subject: PDT-11/150 & RT-11 (was Re: Spacewar, and my pile of burdens...)
Organization: MITS, Helsinki, Finland
Date: Sat, 7 Nov 1992 11:45:24 GMT

In article <9210300201.AA16019@silver.lcs.mit.edu> <cz@silver.lcs.mit.edu> writes:
>
>As to the person with the PDT11: Yes, it is a PDP-11, but an interesting one.
>Basically, what happened was DEC's terminal group wanted to build a nice
>little terminal front end to the microVax. Well, they built 3 models. The
>PDT11/110 was simply a 11/03 CPU in a VT100 box. The 11/130 was an 11/110
>with 2 dectape units stuck below the monitor. The PDT11/150 was a little
>independant PDP11 system with about 32KW of memory, an 11/03 CPU with EIS
>/FIS (and sometimes CUS),2 RX01 floppies, and 6 serial ports. One was for
>th console, one for the modem//link to vax, one to a printer, and the
>other 3 were open for other terminals.

No, my PDP-11/150 doesn't have EIS. MUL, DIV, ASH(C) and XOR all trap.
(Well, I haven't checked XOR) SOB works however.
And few days ago I noticed strange feature:
If I use odd address on word instruction, let's say
CLR @#2001
then processor doesn't trap to 4 (it should, shouldn't it?) but instead
just uses the address with bit-0 masked off, i.e. in this case the word in
location 2000 is cleared.

So, is this a hardware bug or just 'feature'?

>
>Now, the little gem runs RT11, but there is a big catch. The driver for the
>floppy disks is not the DX controller the RX01 used. It was called the PD:
>interface, and it was a Z80 based thingie that could read RX01's. The
>comm ports were also wacko versions of a DZV11 (TP?:) that worked and had
>full modem control. They were controlled by another Z80 CPU. The big bugabo
>was that the thing was a closed bus system. There was no way to put another
>type of disc drive on it (though I know people who tried. A RT11 system in
>that package with a RX01//40MB Quantum 8 inch winchester and 6 ports was too
>much for some people, but it never worked), and there was never a 11/2
>version. Still, it is a great box to run spacewar and space invaders on,
>and it did support the multi term option of RT11FB, so one could run
>VTCOM and RTMON and a RT11 session on seperate monitors (good for a laugh).

Huh, what are VTCOM and RTMON?

>
>Technically, DEC could have sold this as a great PC type system,

Not with those drives, at least not very long...
But I agree that if DEC had understood to develop a micro based on
PDP-11 processor (with competent price!) we could have avoided
that side leap to all those pissy toy-processors, 6502, Z80, etc.
After all, CP/M is just mutilated RT-11. (And MS-DOS is mutilated
CP/M? ;-)

>but DEC being the morons they were, they only sold it as a comm controller.
>I have heard it said that the orig writer of multicalc wanted to write it
>on a PDT11/150, but DEC didn't think it would happen, so he went off to
>Apple. For this reason, I keep it next to my PRO-350 as a testament to DEC's
>lack of vision in the world...
>
>Times change...
>
>CZ

Here is some log from my PDT-11/150:

.SHOW ALL

RT-11FB (S) V04.00  

Booted from PD0:RT11FB
Resident Monitor base is 142740 (50656.)
USR is set SWAP
TT is set QUIET
Indirect file abort level is ERROR
Indirect file nesting depth is 3

PDT 11/150 Processor
50 Cycle System Clock

Device I/O time-out support
Multi-terminal support

Device      Status       Vector
-------------------------------
  PD      Resident      
  LP      Installed      200

TT  (Resident) = CON
PD  (Resident) 
    PD0 = SY , DK , A  
    PD1 = B  
MQ  (Resident) 
LP   
2 free slots

Job  Name  Console Level State    Low    High  Impure
 0   RESORC   0      0   Run     000000 142676 145702

Unit Owner     Type      WIDTH TAB CRLF FORM SCOPE SPEED
--------------------------------------------------------
  0         S-Console DL   80  No  No   No    Yes   N/A
  1         Local     DL   80  No  Yes  No    No    N/A
  2         Local     DL   80  No  Yes  No    No    N/A


.

Heh, I have following commands in my STARTF.COM file, so it's
'easier' to use after using MS-DOS:
ASSIGN PD0: A:
ASSIGN PD1: B:
ASSIGN TT:  CON:

BTW, has anybody written device driver which would allow accessing other
terminal lines than the current one with names? E.g. like TT0: TT1: etc.
 
--
Antti Karttunen / karttu@mits.mdata.fi / $B%"%s%C%F%#!!%+%k%C%H%%%M%s(J
 ++ Think positively, ota olvia, and vote YES!