Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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If a computer uses the 16550a Universal Asynchronous Receiver Transmitter
(UART) for its communication ports, the communications driver will enable
the onboard 16-byte first in, first out (FIFO) buffer allowing Windows to
perform reliable serial communications at speeds of 9600 baud and higher.
(Many computers that do not enable this buffer experience loss of characters
at 9600 baud, and most cannot communicate at speeds higher than 9600 baud.)
 
Before enabling the FIFO buffer, the communications driver checks the
SYSTEM.INI file to determine whether the user wants the buffers enabled. The
COMxFIFO settings in the [386Enh] section of the SYSTEM.INI file specify
whether the buffer for a given port should be enabled or disabled. If the
value of the setting is 1, the driver enables the FIFO buffer; otherwise, it
disables the buffer. If no setting is specified, the driver will enable the
buffer by default.
 
The virtual-communications device (VCD) does not virtualize the 16550a for
non-Windows applications.
 
 
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