Solved Determine Serial speed in DOS

October 26, 2015 at 07:30:09
Specs: DOS
Is there a way to check serial speed in DOS?
how to know if it runs at 1200, 2400, etc?
I am running a DOS program on an old Pentium MMX desktop, but when i move it to a Pentium 4 PC the program does not send correct signal to serial port, may be because of the speed.

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October 26, 2015 at 08:40:21
In DOS the individual programs control the hardware directly. So it is up to your (unnamed) DOS program what speed the serial port is set to. Every program that I have used allows you to set this to whatever speed you desire (as long as the hardware supports it).

(I assume here that you are talking about DOS and not a program running in a Windows command prompt.)

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October 26, 2015 at 19:14:20
Check that the serial port on the P-4 is configured the same as on the P-I. I think the default configuration for most applications was 8-n-1--8 data bits, no parity and 1 stop bit.

Also some old dos applications had a timing problem when run with faster cpus. That might be part of the problem.

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October 29, 2015 at 07:08:14
✔ Best Answer
Hi Jona,

you need to use the dos MODE command to view or modify the serial port parameters.

If you look in files AUTOEXEC.BAT or CONFIG.SYS you should be able to see the parameters as set when the pc boots. Possibly the program itself might subsequently change them.

Obviously the parameters need be the same for both pc and the 'other' device that it is connecting with.

What is the dos program you are having problems with?

Good Luck - Keep us posted.

message edited by Mike Newcomb

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