M98/S4C Serial Port Buffer size

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Hi,
I've been looking through the manuals trying to find the size of the Serial Port buffer, but have been coming up empty....  Anyone got a handle on how much data I can push to the controller from a PC before it starts acting up?  What is the behavior when you reach the serial port buffer limit for M98/S4C/BaseWare 3.2?  Does it drop data, throw an error?

Thanks,
tom