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The 1981 manual for the 8051 contains numerous references to 12MHz. http://bitsavers.informatik.uni-stuttgart.de/components/intel/8051/MCS-51_Users_Manual_Jan8
by dragontamer 3y ago
The 1981 manual for the 8051 contains numerous references to 12MHz.
http://bitsavers.informatik.uni-stuttgart.de/components/intel/8051/MCS-51_Users_Manual_Jan81.pdf http://bitsavers.informatik.uni-stuttgart.de/components/inte...
It was 12T clocked: even though the clock was 12MHz, it would only operate at 1MHz / 1MIPS, because it took 12-clock-ticks to even perform one addition.
IIRC, there was a standard crystal (11.0592 MHz crystal?? I forget exactly) for the communications at the time. So going just above 11 MHz (or really, just above 11.0592 MHz) was needed for reliable serial comms.
- gumby 3y agoWow, right on page 1-2! I'm surprised -- I don't remember anything running that fast back then. Thanks. (Love those old Intel books too) Nevertheless, FWIW, MIPS started out as Vax MIPS, and at first people often used to write "VAX MIPS".
- vardump 3y ago8051 might run at 12 MHz, but actual instructions run in multiples of 12 clock cycles. Realistic code on a 8051 runs only about 450k-800k instructions per second @12 MHz.