What MODE command/utility is this?

Willy wrote on Today, 15:58:

... At start of DOSBox I get a message, that serial mode 9600,5,n,1 is not supported.
At DOS-prompt, >MODE COM2:300,N,8,1 leads also to a message, that serial mode 300,5,n,1 is not supported.

I run an older DosBox under Win7 with serial ports (often USB ones) all the time, at all kinds of speeds, often 115,200 with no problems.

When my edition of DosBox starts, it sez this in the log window:

Serial1: Opening COM1
Serial2: Opening COM2
Serial2: Serial Port "COM2" could not be opened.
Serial3: Nullmodem server waiting for connection on port 23...

No mention of speed or any other assumed settings, and there's no way to tell if assumed settings when starting/

All of my software that talks serial opens and configures the port before trying to use it.

I don't see why DosBox would assume 5-bits by default, but who knows maybe the PC 8250 came up at 5 bits and DosBox tried to emulate that (which might explain the error at startup), but shouldn't occur when you try to use MODE to change the speed to 8-bits. Which leads to a couple more questions:

1) MODE deosn't exist in the older version of Dosbox that I've using- what edition are you using?

3) It almost seems your "MODE" or DosBox itself has been currupted, why when you explicitly say 8 bits is it reporting on a failure to achieve 5?

A couple Q's:

Does it to the same with COM1?

Does it work/fail when you use a program which explicitly opens and configured the serisl?