I have an old Macintosh IIfx and it originally runs with 80 MHz DIP-4 crystal oscillator (CPU speed is half of this, so 40MHz). So far I have used 100 MHz crystal oscillator to overclock without troubles but I would like to push it a little further.
It seems crystal oscillators over 100MHz (like 105, 110, 120) are not cheaply available so I was wondering using a Si5351 or similar to have a programmable clock. Right away there are couple issues: IIfx uses 5V for the crystal oscillator and Si5351 has 3V output so some kind of buffer is required. Also, Si5351 seems to produce quite many harmonics on the signal.
Is Si5351 anyhow feasible choice to replace a crystal oscillator on a computer? Or what would be the preferred way to create variable oscillator for frequencies from 80 MHz to 120 MHz?
Update: Managed to get Si5351 and SN74AHCT125 combo to work at 110MHz. Soldered on a protoboard with short connections. Most likely this would be able to produce higher frequency clock signal but the target machine was not stable anymore due to other limitations.