That can be done with those uCs with about 100Mhz clock and
single instruction cycle.


NONSENSE! The fast MCU will produce a 10 MHz clock only if you do something explicit to force it to do so. With only 10 instruction cycles per 100 ns output clock cycle, it can't really do much else. Would you consume nearly all the bandwidth of your MCU just to produce that one clock?

Nonsense?, well let's have a look
this is a 'speed demon' so no resource restrictions apply
1) the port where the data pin resides has no other use
2) the output is in an array where 6 bits of each byte is unused, one bit, the position of which correspond to the data output pin, is used for data and another bit in the data array is set for all but the last byte.
3)the last bit output will be zero (could be handled but not in the 3 minutes I am willing to spend)

loop:
clr CLOCK    2
mov a,@R0    2
inc R0       1
mov port,a   2
setb CLOCK   2
jz loop      2

OK it is 11 cycles, not 10, but this is 3 mimnutes of development, I guess another hour could reduce it to 10

Erik