SQKYbeaver found a PCIe clocking solution from Silicon labs the he thinks can be hacked into a precision clock generator with multiple outputs:
The Si52144 is a spread-controlled PCIe clock generator that can source four PCIe clocks simultaneously. The device has four hardware output enable control inputs for enabling the respective differential outputs on the fly while powered on along with the spread control hardware pin to enable spread for EMI reduction. In addition to the hardware control pins, I2C programmability is also available to promptly achieve optimum clock signal integrity through skew and edge rate control on true, compliment, or both differential outputs as well as amplitude control.
Actually, you want to use the si5338. It’s I2C programmable from DC to 350Mhz and some selected frequencies up to 710 Mhz.
The Si52144 is 4 fixed rate PCIe clocks at the standard 100Mhz on each channel. Not much to hack
on there.