PDP11/23 More dumb questions

From: Jerome Fine <jhfine_at_idirect.com>
Date: Wed Mar 29 16:57:38 2000

>Olminkhof wrote:

> Well . . . after another few more hours of exploration :
>
> The M8059 YA card wasn't that at all. It is actually an M8639 YA.
> I need glasses . . and stronger light.

Jerome Fine replies:

This makes a LOT more sense. Not only that, but the board is in the
last one in the backplane which is where an RQDX1 must be - since there
is no bus grant on the board to pass interrupts up the line. Not also that
the M8639-YA is an upgraded RQDX1 (or at least that is what I have been
told that the board should be called) and can handle both an RD51 and an
RD52 hard disk drive. The RD51 is usually an ST506 drive which is
10 MBytes and is usually easy to spot because of the actuator arm on
the port side of the drive (left hand side of the drive if you are behind
the drive and the edge connectors are at the back and the front of the
drive is facing forward) right at the front. Incidentally, I have been told
to NEVER touch the actuator arm for any reason at all. The RD52 is
usually (the are 2 other models which were not as popular) a
Quantum 540. If either of these two drives are connected via some
sort of cable arrangement to the M8639-YA, then that is correct.

> Anyway, Control C doesn't work and I can no longer repeat getting to an _at_
> prompt, instead getting a lot of backward ? characters at times.
> I'm now using the console port but have lost confidence in the terminal and
> serial cable completely. I discovered the baud setting control for the ports
> after I blew the dust out of the little window. Set the port to 4800 baud,
> the default setting on the VT220. All for no consistent result. Tried 110
> baud on both with no result

Since you had the _at_ character being displayed for some reason, that STRONGLY
indicates that the VT220 was set correctly for the serial port that it was hooked
to. The characters on the VT220 screen do not become displayed if the baud
rate is extremely different from the correct setting - although they often are
displayed if the baud rate is close. I would suggest the you try 9600 baud
rather than 110 baud.

> I switched to a straight though 25 wire serial cable and got absolutely no
> communication, . . added a null modem and got a little garbage . . changed
> from the default VT200 mode 7 bit controls to some of the others . . . all
> to no result.

If you are getting some characters with the null modem cable and NONE with
the straight through cable, that is normal and to be expected. A null modem
cable IS the standard to be used. If you seem to get a little bit of garbage,
that may be an actual hardware problem OR more likely the wrong baud rate
setting on the VT220. As stated above, garbage is often the result of an
incorrect baud rate which is close. Rarely do you get any garbage at all if
the baud rates between the serial port and the terminal are off by a large
difference. As suggested above, try 9600 baud.

> I think the PDP is booting OK judging by the sounds it makes but there is
> nothing on the terminal screen. The terminal seems to do everything OK when
> in local mode.

Well, that seems to indicate that the VT220 is OK, but naturally you MUST
put the terminal into ONLINE mode if the PDP-11 and the VT220 are going
to communicate.

> I have another VT220 tucked away. Trying that is all I can think of at this
> point. I should see something on the screen even if the hard drive or OS
> have a problem shouldn't I?

Not necessarily. With some boot ROMs, the first thing to be displayed is the
PDP-11 saying which OS has been booted.

> Is there a PDP11's for Dummies book?

YES! It is all blank pages. Sorry! If a PDP-11 is working, it is usually
not too difficult (especially with RT-11) to type in HELP and see what
commands can be executed. But if there is any trivial problem (like
maybe you do not have a hard disk drive), it is extremely difficult to get
going in the first place.

See how setting the baud rate to 9600 for the VT220 works.

Sincerely yours,

Jerome Fine
Received on Wed Mar 29 2000 - 16:57:38 BST