asrock h81 pro btc - 6th gpu problem

csf707 wrote: I'm having issues booting with 6 gpus, any guidance in this area? Boots no problem with 5 but as soon as I add the 6th, it goes in a boot loop error problems starting windows 10. I tried using Gen1 & Gen2 in bios without success. They are all on PCIe risers, powered by their own molex cables for each lane. And mobo's 2 molex connectors are also plugged in.

Most likely its the usual out of reserved memory problem when using many video cards.

Windows reserves some of the DRAM memory for hardware use, but only a certain amount is set aside. Once all that reserved memory is used, there is no more room for another device, and either Windows does not boot or it does boot but the device will not work. The amount used depends on the video cards you use, some use more than others.

You can check that when you have five cards connected, boot Windows and go into Resource Monitor, and see how much is Hardware Reserved in the Memory tab.

Check in the Chipset Configuration screen in the BIOS, if you have an option called "IOMMU...". If you do set it to enabled. That option can increase the amount of reserved memory for hardware.

How much memory do you have in that PC, and are you using the 64bit version of Windows 10?