Advertising raw
clock speed, instead of bus speed.
IBM uses raw clock speed as the speed of the computer. In
the
IBM PC and
IBM PC XT, the clock is divided by 4 to
produce the 4-phase bus clocks. Thus a 4 MHz IBM XT really
runs at 0.895 MHz, because that 4 MHz was really 3.58 MHz
which gets divided by four.
A
Tandy Color Computer ran at exactly the same speed, but
clock speed was specified as bus speed, 0.895 MHz, leaving the
impression that it was 4 times slower. Actually it ran a
little faster with a more efficient
instruction set. If the
actual
clock rate had been specified on a CoCo 3, it would
have been 14.32 MHz, although the bus speed was still 0.895
MHz. That high speed also generated video, color, and hidden refresh timing.
100 MHz computers are running at bus speeds of around 25 MHz.