Michael J. Mahon wrote: > My mistake--the copyright date on the card appears to be 1978 (1976??), > and the earliest preliminary 6551 datasheet I can find is 12/80! The 6551 was not the first ACIA or UART to be released. Intel had the 8251A (preliminary data sheet dated 1978) and Motorola had the 6850. > So apparently, UARTs weren't available when this board was designed! This may be true.