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What version BIOS do you have? It should be on a sticker on the BIOS chip itself (I'm assuming a new part and not second-hand).

Older 100 based boards that launched with the 6th Generation Skylake CPUs need BIOS updates to run with 7th Generation Kaby Lake parts like your i7-7100. I think you need BIOS v7.00 to support Kaby Lake CPUs in that board.

Do you have a Skylake you can use to update your BIOS?

d3aths wrote: Unfortunately I dont have any spare CPUs I can use to do that with. Ive been googling around about it and I know theres a bio update on the asrock site I could flash on from USB, but would that require the skylake to be installed first or is it possible to do with the non-posting cpu? also the only thing on the bios sticker just says P2.50?

As said above, at least the 7.00 UEFI/BIOS version is required in the board in order to use any Kaby Lake processor. That is one definite known situation why the PC is not working, POST if failing with your CPU and UEFI combination. You cannot do anything until you have a working CPU and UEFI combination in the board, including any type of UEFI update. But please keep reading...

Since the board is new (correct?) the UEFI version on the sticker (P2.50) is the one in the chip.

Besides using a Skylake processor for the UEFI update, if you could borrow one somehow, you only have one other option. Replacing the UEFI/BIOS chip with one that has at least the 7.00 UEFI version in it. The UEFI chip on your board is replaceable, it is in a socket, located between the copper chipset heat sink and the SATA ports. The chip can be removed and replaced without soldering, but must be done carefully, with either a chip removal tweezers type tool or a very small blade screwdriver to pry it out of the socket. Be sure to remember the orientation of the text on the chip so you replace it in exactly the same way.

You can order a replacement UEFI chip from ASRock by submitting the form on the Repair/RMA page on their website. You must clearly explain the situation when filling out the form, although you are certainly not the first person that has ordered a replacement UEFI chip for this reason. Meaning support should understand the situation. You need a replacement UEFI/BIOS chip for your Skylake chipset board because you only have a Kaby Lake processor. FYI, this is a limitation from Intel and affects any mother board made by any manufacture.

http://www.asrock.com/support/index.asp?cat=RMA

I cannot guarantee this, but ASRock might send you the chip for shipping charges only. When you submit the above form, you should initially receive an automated email response from ASRock that confirms your form was received. If you don't get that email, something was wrong with your email address and you must submit the form again.

It is also possible to get the UEFI chip from places like eBay, with the correct UEFI file on the chip. I cannot suggest any specific source, but I know of other people whom have had success using those chips.

Newer ASRock boards no longer use the replaceable UEFI chips, as they are no longer available from the chip manufactures. You need to get this done while it is still possible.