GA-Z77X-UP5 TH -- SATA Drives spin down when not accessed for a while - feature or fault?

[nickweavers]

Hi, this weekend I rebuilt my PC with a GA-Z77X-UP5 TH motherboard, an i7-3770K CPU, 32GB of Corsair Dominator DDR3 RAM and a 480GB SanDisk SSD. I kept my CoolerMaster 850 Watt modular PSU and 4 Hitachi Deskstar disks (2x500GB and 2x1TB).
After a fairly straight forward install with just the SSD connected to install W7 Pro on, I spent most of the day reinstalling all my software packages and configuring them again. I had to reboot many times and the boots all went without any hitches except that I had to switch off the PSU for 30 secs or so before booting up or the monitor would report "No signal". This seemed to be resolved by replacing BIOS version F4 that came loaded with F9 from the GigaByte website. While downloading the latest BIOS I grabbed all the drivers too and updated those.
However, when I started to hook up my SATA drives, all hell broke loose with BIOS loops that didn't complete to POSTS even after disconnecting the SATA drives again. I eventually followed the advice posted here to strip back to just the board and try to get things stable again. This worked and I am now back to having just a couple of the SATA drives connected, but if I connect a third the disks start doing weird things, randomly spinning up and down, clicking and making alarming sounds. With just two SATA drives the system seems stable but I have noticed that when the disks haven't been accessed for a while they spin down. As soon as I try to access a file on them they spin up again.

Is this a power saving feature? I am not a regular PC builder - just rebuild every couple of years to keep up, so sorry if the question seems a bit daft. I realise that the disks will spin down when the machine goes to sleep if not used for a bit, but it seemed odd to me that the disks themselves would spin down even though the keyboard and mouse are in use. I just thought I would ask before suspecting my PSU or the drives themselves as both have been fine until the rebuild.

TIA for any advice or education you can give me... I feel well out of my depth here.

[wazza300]

its normal for them to power down to save power,soon as you access them they whine and click and spin into action,you can turn it off somewhere in windows

as for the other issue with 3 or more drives i have no idea?

[nickweavers]

Thanks wazza300. I had never noticed that Windows was doing turning the disks off before, but just found the setting after you pointed it out.

I have a new power supply coming (Corsair CMPSU-750AXUK Professional Series Gold 750W) so will see if that makes a difference to the problem with more than two disks.

[Acebmxer]

F11 is the latest bios and it can be found here GIGABYTE Latest Beta BIOS

[nickweavers]

Thanks @Acebmxer. I'll give it a try.