>> I make diode testers and need an operating system that is close to "real
>> time". Also I need to sometimes interact directly with the computer
>> hardware. FreeDOS fills the bill on both counts and WINDOWS is useless.
>> I appreciate very much what you folks are doing and hope that I can help
>> in some way.
>> I program in FORTH using a FORTH Interpreter/Compiler that I wrote
>> myself in assembler.
> This is a way-out-there what-if, but anyhow...  How much trouble would it 
> be to make FreeDOS explicitly realtime?

I think what he meant is that because DOS does not put a compulsory
layer between you and the hardware and because DOS does not waste
CPU time in the background, DOS already *is* close to real time and
already lets you interact directly with the hardware. Of course you
have to be aware that when you do file I/O with DOS, it can take a
while - so you would only let DOS do work for you when you are not
in a real-time situation. You can for example measure your diodes,
without accessing DOS, in real time. Then, when the measurement is
done, you can use DOS to save the results in a file. At that moment,
it is no problem that DOS will spend an "unpredictable" amount of
time writing the file before it returns control to the caller, in
this case the diode tester. Note that some unexpected time-wasters
exist: For example USB mice using BIOS PS/2 emulation can have much
more lag in DOS than actual PS/2 mice. Just in case you would want
to measure, say, reaction times by timing the moment of clicking.

Regards, Eric

PS: Of course it is much more exact to use directly accessible I/O
bits for time measurement, such as parallel printer port pins, the
joystick port buttons or the serial port status lines.

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