Hi. Could you provide us with your computer's specifications. If you're not familiar with how to do this go to piriform.com and download Speccy.
As you can se on the pic to the right (CPU-Z) I have a core i7 4790K running at 4,5Ghz, 16 Gbyte ram, ASUS Maximus Ranger VII mobo, Samsung 840EVO SSD. Do you need to know more?
Read some threads where this happened in Windows 8.1 and flashing the BIOS fixed a few of them. You can check to see if there is a BIOS update for you system at the manufacturers web site.
No new BIOS for my mobo. But I disabled "Intel Speed Step" and "Intel Turbo Mode" in BIOS under "CPU settings", and then it installed :-)
That was the next things I was going to suggest you try
Seems like "Intel Speed Step" is set too aggressive and installation didn't manage to load it up enough to jump over 1 GHz.
I think MS has to look into this install procedure again ...
I believe MS recommends removing any overclocking before install one of their OSes. Put it back once done.