[SOLVED] PC fails to boot after CPU swap

[skeet34]

I built my gaming PC about a year ago and it has been working great. I recently purchased a HP Omen gaming PC for my son and after ordering a new AIO cooler and some RGB fans, I decided I was going to swap out his i7-8700 for my i7-6700 to get a little CPU boost and a couple more cores (4 to 6) to go with the cooling upgrade. I made sure to clean off the chip and cooler in doing the swap to get all the old thermal paste off and everything went smooth...or so I thought. When trying to boot up his PC, all the fans and RGB lights go on for about 10-15 secs and then the PC restarts and this process will continue until unplugging the power supply, never sending a signal to the monitor. My PC on the other hand has all the fans and lights come on for about 1 sec and then shuts down. I did a ton of research in trying to find a solution to no avail and have since put the old CPUs back in their original systems and booth booted up and worked perfectly. So, here is what I have done so far while trying to figure this out.

1. Ensured that all the pins on for the CPU are not bent or messed up in any way.
2. Thoroughly cleaned all old thermal paste before reapplying
3. Cleared CMOS on booth systems by using jumper and removing CMOS battery (his PC said it needed to reset CMOS or something to that effect after old chip went back in after I gave up, while my PC just booted up with no BIOS promts)
4. Yes, the CPU fan is connected

I spent 6 hours dealing with this all today and I'm at a complete loss. In my experience and everything I have read, a CMOS reset should have solved my issue but it did not. The fact that the CPUs are both working perfectly in their original systems tells me there is not a hardware issue. I still believe it has something to do with the BIOS, but I have no idea what or why?
Any and all help is greatly appreciated! Thank you!

 

[richiestang_78]

A 6700 motherboard will not work with a 8700 or vice versa, although both are 1151 sockets, the 8th gen and up Intels are 1151 (300) series which while dimensional the same are not comptible.

 

[skeet34]

Well that explains it. I haven't done any real PC building in over a decade apart from mine last year. That obvious fact didn't even cross my mind. Double checked and my H170 only supports 6th/7th gen. I feel like an idiot, talk about learning the hard way lol. Thank you for your help!