Rodrigo Cesar Banhara wrote in a message to Leonard Erickson:

 -=> Quoting Leonard Erickson to Roy J. Tellason <=-

 LE> The 2000 has some nice features, such as using USARTs instead of UARTs
 LE> on the COM ports. And 640x400 graphics (2 color or 16 color depending

 RCB> mm... interesting, but what the difference between these UARTs? 

The "S" indicates that the part is capable of "synchronous" operation,  which
means that instead of start and stop bits it uses other means for the two ends 
to coordinate their operations.  Since you aren't sending those extra bits for 
each byte getting transferred,  it's faster. 

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