[Simh] MAME and simh

Wed Jul 8 14:56:31 EDT 2020

Hi folks,

With help from Gus Del Dago, I have got mame to talk to simh, so as
promised, here is my recipe for doing this.

I have done this on a Debian 10.1 system.
I installed mame with 'apt-get install mame'.

Gus sent me two files. They are both called vt240.zip.
The first file is the ROM image that mame usually needs. I had such a file
already and I need to go back and check if my original file was 'fit for
purpose'. I have placed this file in the sub-directory MAME/Gus/roms of my
login directory.
The second file is an image of the surroundings of a VT240 terminal. I have
placed this in the sub-directory MAME/Gus/artwork of my login directory.
The second file is not required, but it does give a pleasingly retro
appearance to the emulated terminal.

The simh system that I am connecting to is a simulated microVAX 3900.
My vax.ini configuration file finishes with the lines

; Allow telnet connections to the DZV11 serial interface
SET DZ LINES=4
ATTACH DZ 10003
; Start the CPU
SET CPU CONHALT
DEP BDR 0
BOOT CPU

This allows me to connect to one of the asynchronous serial ports.

Alternatively you can connect mame to the simh console with
SET CONSOLE TELNET=10004

In the latter case, remove the SET CPU, DEP BDR 0, and BOOT CPU lines from
vax.ini and boot the microVAX from the emulated VT240.

The port numbers 10003 and 10004 are arbitrary.

I start simh with the command
./vax

I wait for the boot sequence to finish, then I start mame with the command

mame vt240 -rompath /home/peter/MAME/Gus/roms -artpath
/home/peter/MAME/Gus/artwork -window -vol -15 -bitb socket.localhost:10003

A large window appears simulating a VT240 screen. At first 'Wait' appears
in the top left of the screen. Then 'VT240 OK' appears in a box. This is
the usual behaviour when turning on a VT240 terminal.
Then you get some garbage characters on the screen being sent from the
microVAX. This is because the baud rate of the mame terminal is set to
4800. To change the baud rate, do the following:

Press F3 on the keyboard. This gets you into the SETUP menu for the VT240.
Press Enter on the keypad (not the normal Return key) three times and press
the right arrow key twice to get to the Transmit speed box. Pressing Enter
will increase the speed from 4800 to 9600.
You can save these options for the next time if you wish.
Now press F3 to exit from the SETUP system.

Now press the normal Return key. This will give the 'Welcome to OpenVMS'
message allowing you to log in.

I found the scroll speed to be slower than I liked, so I went back into the
SETUP menu and changed the Smooth Scroll option to Jump Scroll.

I am happy that I have cracked the basics of getting mame to talk to simh.
I will look further into using mame to emulate VT terminals later. I like
the cool retro appearance of the screen (and I know that some terminal
emulators can do this too).

Finally, a few words about why I had difficulty getting this to work in the
first place. I mention this in case anyone else gets caught out the same
way.

The instructions that I have given are essentially the same as I had
already found on the internet. In my first attempt, I must have made some
silly error in my ignorance. (No surprise there.) What sent me down a
rabbit hole is that having failed to get the vt240 option to work, I just
tried replacing vt240 in the mame command with vt100 (or perhaps vt102).
This gave the error message
Error: unknown option: -bitb

So I started reading the man page and the documentation looking for an
explanation of the -bitb flag. I found no such explanation and concluded
(erroneously) that the -bitb option no longer existed.

What had not occurred to me was that -bitb is a valid option when
specifying vt240 as the system to be emulated, but that it is invalid when
specifying vt100 as the system to be emulated. In my experience, Linux
command lines do not usually work this way! Ah well, you live and learn.

Cheers

Peter Allan

On Wed, 1 Jul 2020 at 14:34, Peter Allan <petermallan at gmail.com> wrote:

> Hi folks,
>
> I am trying to get MAME to talk to simh in order to use MAME as a VT
> terminal emulator. However, I am failing to get the two to talk to each
> other. I have been using simh for over 10 years, but I only picked up MAME
> two days ago.
>
> I have tried MAME v 0.222 on Windows 10 and MAME v 0.208 on Debian 10.1.
> Both start up successfully, but I have trouble using them. I also have a
> set of 13 ROMs for several VT terminals.
>
> I have found some helpful information on the web, specifically
>
> https://zork.net/~st/jottings/Real-VT102-emulation-with-MAME.html
>
> and
>
>  https://wiki.mamedev.org/index.php/MAME_and_SIMH
>
> The latter page looks like it should be just what I am looking for, but it
> describes using a VT240 ROM. My vt240 ROM doesn't work. My vt220 ROM does
> work, but when I follow the instructions to 'press F3 to enter setup',
> nothing happens.
>
> I have also got the impression that some of the command line options for
> mame have changed over time, so some older information on the web may no
> longer be accurate.
>
> So, has anyone got this combination to work? If so, can they send me exact
> instructions on how to do it please. I hope that I am simply failing to do
> something that will become obvious with hindsight.
>
> My normal Linux system is CentOS 6, CentOS 7 or Fedora 31, but I also have
> Debian 10.1 available.
>
> I run several simulated VAX and PDP-11 instances using simh.
>
> Cheers
>
> Peter Allan
>
>
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