The solution is to buy an ASIC miner? This is a bitcoin forum, not sure why you are talking about PC parts.
Not really. This is indeed after all the altcoin mining sub-forum. There should be no discrimination when talking about PC parts for mining especially when a well built altcoin mining rig earns more than some ASICs.
Going back to the topic and helping the OP, you could try checking your miner's log file. Make sure you turn on logging or debugging if you haven't done so. If your PC only freezes after turning on the miner, most likely you will find an error on your miner's log file. If you can paste the contents of the log file here we can take it from there.
Lol, the moderator might already moved this topic to altcoin section.
Is there any solution proposal other than this?
Have you tried installing the single GPU in PCIEx16 slot without using riser? what's the result?
Try to do this with your 1070, if it fails, clean uninstall driver then install using GTX1070.