Almost certainly it uses a 16550 type UART, thus it has a 16-byte receive
FIFO. This is not the size of the buffer that is used by the serial port
driver, however (and you or I have no control over the FIFO usage, as we do
on a desktop system).
The real question is why do you want to know? Perhaps there is an issue
that doesn't involve the FIFO?
Richard Grier (Microsoft Visual Basic MVP)
See www.hardandsoftware.net for contact information.
Author of Visual Basic Programmer's Guide to Serial Communications, 4th
Edition ISBN 1-890422-28-2 (391 pages) published July 2004. See
www.mabry.com/vbpgser4 to order.