I'm sure that the all-knowing, all-seeing Erik Malund knows what the O/P wants and needs, though he hasn't clearly stated it, particularly when it is clear he meant crystal when he wrote crystal oscillator.

As far as I know, if you triple the oscillator frequency, irrespective of how you generate that oscillator, and feed it into the MCU, it will cause everything to happen at three times the rate, if that rate lies within the capabilities of the MCU. What part of that is incorrect?

The O/P clearly stated, "The microcontroller I use is an AT89S51RC. As far as I can tell from the data-sheet it has no internal timer and can be used with a crystal between 0 and 33MHz. I connected the crystal between pins XTAL1 and XTAL2 and connected connected both pins to the ground using 30pF capacitors as instructed in the data-sheet." From this latter portion, I'd infer that he's connected a crystal to the MCU, though the capacitor value is rather large for a high (>15 Mhz) frequency. The majority of cases I've seen operating at >25 Mhz use 3rd-overtone crystals, and those oscillate in fundamental mode at nominally 1/3 the 3rd overtone rate. That seems to fit the symptoms described by the O/P.

From which portion of the O/P's query would you conclude what he "needs" or doesn't, Erik?

Which portion would you label as "invalid", o all-seeing, all-knowing one?

RE