Hard disk spin-down
I don't think OPL does this already. Before powering off, it's important to spin down any attached hard drives.
There are other situations where spin-down would be useful:
- An option to stop the HD while remaining in OPL would be nice; the user can then unplug it, take it to a PC and put more games on for example.
- Also, if OPL ever has an option to start the game disc in the PS2's DVD drive, an option to spin down the attached USB HD first would be good.
When power is disconnected from a spinning hard drive whose heads are loaded, an emergency unload is performed. That is bad for the drive, and it happens every time the PS2 is turned off. A drive might be rated for 600,000 normal load/unloads, but only 20,000 emergency unloads; an emergency unload causes the same amount of wear as 30 normal unloads. For details about this, see page 30 of the manual for one type of Hitachi hard drive:
Whether it's possible to unload the heads of a USB hard drive depends on the firmware of the (S)ATA bridge chip. Usually, issuing a START/STOP UNIT command works. Maybe it's also possible to tell the USB device to suspend, and remove power from the USB port? That might work with some drives which don't obey START/STOP UNIT.
For some mains-powered (3.5") USB drives this isn't really a problem, since they spin down automatically when the computer (or PS2 in this case) is turned off. But that doesn't apply to all 3.5" drives, or any USB-powered 2.5" drives.