Hi people,
I need some help to understand the PCIe clock frequency on host PC's.
According to PCIe Sig, the PCIe clock frequency should be 100 MHz +- 300 ppm. Then, to follow this recommendation, i configured a SIlabs 5338 to synthesise precisely 100 MHz and used it to feed the FPGA Transceivers of Altera PCIe Hard IP, i'm using local clock reference on my project.
The result was that my project do not worked! I could not establish a communication with my board and linux do not recognized it.
After make a lot of tests, i found that the PC was generating 99,7~ MHz as a reference to PCIe, i measured it in the motherboard, what is out of 300 ppm range. I measured 3 diferente PC's and all of then had the same value .
After i configure silabs with this value the system started to work.
the question is: why PC's use this frequency and do not PCI Sig recommendation?
Thank you,
