Cannot Add 5th card

I'm building a rig with all 3070 cards. The motherboard has 6 PCI slots. I can fill 4 of them without issues. When I add the 5th card it starts up, then shuts down within seconds. This repeats until I power off the rig. I have disconnected all the drives, then tried to add them one at a time. Still, on the 5th one, it crashes. My friend has this issue adding the 8th card. Any ideas?

change the usb cable, or the riser, is most likely

I forgot, if you have a single power supply, you better put two 800W ones, at first to save money I used the cheap ones, use power supplies that have 4 PCIex outputs

I have switched cables/risers with the other cards. Tried different slots on the MB. I do have an EVGA Supernova 1200P2 PSU I'm using. I'll connect another PSU to the 5th card and test it out. Thanks!

If you are still having problems you can try......

Enter Bios
Go to advanced tab
System Agent (SA) Configuration
Graphics Configurations – Change primary display to CPU graphics
Back out one
PEG Port Configurations – Change PCIEX16_1 and _2 Link Speed to Gen2

Back out to advanced tab
PCH Configurations
PCI Express Configurations
Change PCIE Speed to Gen2

Back out to advanced tab
PCH Storage Configurations
Disable all sata Ports except the one your SSD is in

Back out to advanced tab
PCI Subsystem Setttings
Make sure above 4G decoding is Enabled

If switching to gen 2 doesn't work then try gen 1. Different MB bios look a little different so the settings may not be exactly where this lists them. You may have to look a little bit for them. With these setting I have 8 GPU running on each of my rigs and have not had an issue from day one.

Wow, very detailed explanation for resolution! This worked for me and hopefully, others will see this post. I have found a lot of posts with no resolution.

Happy I could help Be sure to tell your friend too maybe he can get his 8th working as well.