CPU Mark Score much lower than expected: I've checked all the normal reasons

[Rynchor]

I recently noticed that my computer seems to be maxing out on CPU for relatively simple processes: I was noticing the computer slow down with multiple Chrome tabs open, and if I even try to play a simple game like Hearthstone, I can watch the CPU sit at 100%.

I built this computer about a year ago, and I don't use it very much (only has about 300 hours of usage so far).

I downloaded PassMark to see what was going on. All of my scores seem correct except for that of my CPU. Here are some system specs:

i7-6700
Gigabyte Z170-Gaming GT
32 GB DDR4 Kingston
Samsung 850 Evo SSD
Nvidia Geforce 1070 GTX
Corsair RM850X

Here are my PassMark scores, what I tested and what Passmark says I should be getting for that component:

Component/My Tested Score/Internet Average Score
CPU/7790/10036
GPU/11500/11027
RAM/2805 (93rd percentile)
Hard Drive/5117 (96th percentile)

So you can see that all of my components are performing up to standard, except for my CPU, which is woefully slow (it is scoring low than mobile CPUs from a couple of years ago!)

I've checked all of the normal things.
-Looked in the BIOS, everything looks fine, memory is running at the right speed, I have everything at default (no overclocking).
-Disabled all startup programs
-Temps look great. CPU running at a nice 36 C, I have a big Noctua heatsink
-I've had Bitdefender on this system since the day it was born, scans reveal nothing

What else could be the problem? One thing is that the built in sound on the Gigabyte board has been useless since the day I built it, to the point that I had to buy an extra sound card. It constantly was putting out lots of noise as well as the normal audio. Perhaps that is related? I'm doubtful.

Thanks for any help.

[David (PassMark)]

See this post to start with
Causes and Solutions for a slow PC

Also run the test a few times to see if the results are always consistent (it might be a background task that only gets busy from time to time).

Also see if you can identify if all the tests in the CPU test suite are slow, or just one or two of them. For example there as been this issue with just the floating point test.