System fails to boot when attaching more than 4 internal HDDs

[demiankz]

I'm stumped.

My 100%-working previous set-up had:

1 System HDD
1 System Backup
1 Time Machine Backup
1 Cache drive
2 drives formatted for RAID1
750W PSU

Six HDDs total. System booted fine. All drives mounted and read/writable.

Then my system drive failed.

 

I reformatted it and restored it from my backup (so, identical to the 100% working system before the failure). Everything's hunky dory EXCEPT now whenever I attach more than four internal HDDs:

• I cannot access BIOS.
• I can see the BIOS splash screen, but I can't enter setup. I attempt to press Delete, but the screen simply goes black and, I'm assuming, the BIOS starts to look for a HDD with an OS on it.
• Clover bootloader fails to load.

It doesn't matter which configuration of SATA cables, drives, or SATA ports I use; whenever I plug in a fifth drive, no matter which one it is, which cable I use, or which port it is plugged into, the system hangs.

I purchased a new 850W PSU. Overkill for this configuration, even with 6 HDDs attached. No dice. Same problem.

Any ideas? Thanks.

[smolderas]

Reset BIOS, if that doesn't help, try to identify the problem with detaching drives one by one and booting the system.