Welcome to the forums Malurth
 
Sorry to see your X99 Classy is being difficult
 
Lets see what we can do
 

Malurth
If you leave it on, it displays a few codes around the high 6 to low 7s range, then slowly increments to 99, where it hangs for a while before repeating the process.

 
This is probably the CPU temp
 
Please list your build details
 
CPU
CPU cooler - where connected to MB
PSU - what is connected
RAM - specifices
GPU - how power is connected which PCIe slot
 
Have you tried clearing the CMOS ?
Are you following the manual for all connections -- especially which RAM slots to use ?
 
Have you confirmed the PCIe switches - cycle them Off then back On ?
 
 
 
 
 
 

Well, I know the gpu works because I've been using it in my previous PC.

As for parts, I don't have super specifics on most since this is hardware gifted from a friend, but here's the best I got:

Cpu: Intel i7, something close to 7500k I think
Cpu cooler: it's a corsair h60, with the 3-prong cable connected to the nearby 'cpu fan' part of the mobo; backed by fans on the case drawing power right from the PSU.

PSU is a rosewill glacier 850w, connected is the main 24 pin to mobo, both 8-pin wires to the two ports for them above the cpu, 1 sata power cable, 1 pcie for the gpu, and 1 4-pin molex connected to the case fan replacements.

Ram is 4x hyperX predator ddr4 ram

Gpu only has 1 8pin pcie port, so I connected the pcie PSU cable to it

I haven't tried clearing the cmos, not sure what that is. Should I?

I have followed the manual to the best of my ability; ram was slotted in 1,3,5,7 and now just 1 to try to get it to boot

I'm not familiar with pcie switches, so I haven't done that either.

Finally I thought you may be right about cpu overheat, since earlier I had forgotten to hook up the case fan replacements which feeds into the cpu cooler, and I noticed the tube was quite hot. But it's still doing the same thing even though I left it off for over an hour.

What TIM did you put between cooler and CPU
 
PCIe switches -- look this over   https://www.evga.com/products/product.aspx?pn=151-HE-E999-KR
 

Make sure that the drive(s) are set to the correct option in BIOS (AHCI or RAID). Double check that you have the boot order selected to the correct drive. If you get the A2 code try hitting F1 and see if you get a different code. Let us know what you find.

Malurth
I put some Cooler Master thermal paste between the cpu and cooler.

Thanks for the info on pcie switches; though they still have the protective covering over them (and my gpu covers them anyway making them kind of impractical but I guess that's irrelevant). So should I remove the gpu, the covering, cycle the switches, put the gpu back on, and reboot?

 

Yes, after unplugging PSU - then hold start button 20 -30 seconds to discharge capacitors. 
 
Use a ground strap or at a minimum touch the case before touching the parts inside
 
When you placed cooler on CPU
1) did you keep the cooler level during the tightening of the 4 retainers ?
       Turn them a little at a time in an X pattern. maybe 1/2 turn, move across to other side ....
 
2) When did you stop tightening the retainers ?
        Usually 1.5 - 2 turns past the cooler sitting against the CPU is enough - as the springs just need to be compressed a little bit
 
3) What do the little springs that push the cooler down look like ? 
     The wire coils should still have visible open space between them.  If the coils are touching then it has been over tightened
 
If the CPU cooler is over tightened or not kept level, the pins in the CPU socket on the MB can be forced out of alignment
 
-- Confirm that all switches are in the default position
 
-- Confirm that all PSU power cords are fully seated & locked on both ends if you have a modular PSU

Solved: turns out I'm an idiot, actually.

I thought I had just one DVI cable, so when I confirmed I had 'it' plugged into both the monitor I was using and my PC, I assumed that could not be the issue, as I had been using the cable with no issues.

Cue facepalm when I realized I have two, and had both plugged into thin air instead of each other.

Oh man...

Stuff happen..... learning lesson ... why we usually ask people to check the basics first
 
Watch those CPU temps
 
Have fun with your X99 Classy
 
maybe edit your first post .... edit title to ADD the word Solved