Dear Eric,

standart 8051 microcontrollers has machine cycles which consist of 12 osc. cycles. That means if you use an instruction that runs in 1 machine cycle, it takes 1 usec (microsecond) if you use 12 MHz crystal freq.

When you use 11.0592 Mhz then it takes a bit more (apprx. 1.085 usec.).

Now it's obvious that you can't produce
1 MHz output from any port pin by software. Maximum freq. can be apprx. 500 KHz.

ALE and PSEN signals are 1/6 of Osc. Freq. that means apprx. 2 MHz.
But you have to be careful when using these signals as a clock source because
they're not designed for that purpose.
You have to consider fan-out.

Best regards.

Selim Dilmac