[Simh] Extended SimH on BeagleBone controls real blinkenlight panels

[Nathan Cutler]

> Also, I have simh running on a SheevaPlug plug computer under Debian linux which provides a UART and USB for serial connections (it has no PC type console). I use a serail terminal emulator as the console, but If I had a Decwriter or a teleetype it would work.

If I remember correctly, the SimH serial-port emulation relies on
telnet. Awhile back I tried to attach a real VT420 to a SimH/VAX
instance running OpenVMS 7.3, and as I found out it's not really the
same as running a VT420 attached to a real VAX. To gain access to SimH
using the VT420, one first has to get the VT420 connected to the host
computer (running Linux in my case, so I used the computer's serial
port and a serial console - getty). From there, one must telnet into
the VAX, either using OpenVMS TCP/IP Services or using SimH's
serial-port emulation.

No matter which way I tried it, the Linux telnet code caused various
glitches and annoyances. Eventually I did get it to work
satisfactorily, but only at 9600 baud. All the gory details (which I
no longer recall) are archived for posterity on comp.os.vms.

In the end I found that the best results came when I used LAT instead
of telnet. Linux supports the LAT protocol via LATCP, and of course
OpenVMS supports it natively. Bottom line: avoid telnet.

While we're in "wish list" mode, I'd like to see SimH emulate Alpha or
Itanium, so I could use it to run  newer versions of OpenVMS than 7.3.
There are free versions of commercial Alpha emulators available, but
they only run on Windows (BLEAH) and their performance is
intentionally limited, presumably to get people to buy the full
version.