When the LaserWriter's input buffer fills, it sends an XOFF character to
the computer. In some cases, after receiving the XOFF character, the
computer can't stop transmitting immediately. This means that if the XOFF
character is not sent early enough, characters may be lost.
The LaserWriter sends the XOFF code when there are 100 characters left in
the input buffer. If this is not enough, changing to version 2.0 ROMs may
help. Those ROMs support DTR as a method of handshaking, which generally
operates faster than XON/XOFF.