"because a usb device is drawing too much power"

You could try getting a powered USB hub so the computer wouldn't be the power supply.

Hi,

I would also open System Profiler and check the Hardware > USB section.

You may find you can determine which external sockets are connected to which controllers.

Not all external Ports lead to the same Controller.

That controller is likely to be handling both External and Internal devices like the Blue Tooth or Internal camera if your PowerMac has one.

You may also see the Keyboard as the the two ports there if you have anything plugged into them.

The "drain" so to speak may not be just External ones although unpowered ones can make the difference.

It might be a symptom of the Controller breaking down.

9:57 pm Sunday; April 24, 2016

Hi,

I am not aware that any one file or .plist holds this info but it is a possibility.

Reset the PRAM How to Reset NVRAM on your Mac - Apple Support (it is called NVRAM on Intel chip computers but the keystrokes are the same).

9:16 pm Friday; May 6, 2016

Using a PowerMac desktop computer

Mac OS X (10.7.5), 16 GB 1333 MHz DDR3

????? They can't run Lion.

Power Macs don't use Intel CPUs, Lion only runs on Macs with Intel CPUs.

You may be confusing Power Macs with Mac Pros, some of them may look externally similar, but they are not the same.

You don't have a Power Mac, if you're using Lion, you have a Mac Pro and have been just using the wrong name for it.

The last Power Mac was introduced in early 2005.

Hi,

That does not list an Camera which would suggest a Mac Pro (big Desktop Mac commonly referred to as Towers).

Only the Mac Mini and Mac Pro do not have cameras.

The Display though does have a Camera. (iSight, which might suggest the display is somewhat older)

Each Line in the top right box of your pic will reveal other info (If anything is connected) in the bottom right hand box.

This one hub controls an External Port which has the External Hub and in turn the iPhone and a USB Mouse - then a second External Port with my Logitech AK5370 external Mic followed by the internal connection to the Blue Tooth (BRCM2046 Hub) and then the Blue Tooth device itself.

There may be some name changes as USB 2.0 was at one time "Highspeed" and now you can also get USB 3

AS some of yours don't appear to list anything I guess you have USB ports on the back and front of the tower that don't have anything plugged in to them.

This one from my G4 (PowerMac) computer has this

The Hi Speed here is USB 2.0 that is added be PCI card (Expansion Slot) which then has a camera plugged in.

My Older Studio Display also has USB ports in the back but there is less plugged in now than when it was my main computer.

From there:-

In some cases they may not tally.

In some cases you may have to add up the figures for the devices attached.

8:42 pm Friday; May 27, 2016

Hi,

Add them.

From the same hub you have the two you have Highlighted.

One uses all the 500mA and the keyboard uses another 20mA

Pat of that is because the Display has some of the items connected to the "base" hub for USB and the power is probably not coming via that hub itself.
The Display is effectively a powered hub in itself.

the Keyboard is not and is only USB 1.1 (Note the speeds).

Do the Display Audio and Camera exceed the 500mA listed ?
And what does the Display item itself say ?

Is there a Printer in all of this ?

It is late where I am and it will be a while before I post again.

9:52 pm Friday; May 27, 2016

Wow, this won't solve your USB power issues, but I would recommend upgrading from Lion. Lion is probably the least favored OS X versions after Snow Leopard. The memory management enhancements introduced starting with Mavericks, are worth the upgrade all by itself.

Have you considered getting a powered hub, which should fix your power problem?

Technically, you should have a full backup of your current system, preferably a cloned backup, before upgrading an OS X. If you had such a backup, there would be no risk in trying out an upgrade, i.e., El Capitan, as Mavericks is no longer available (unless previously downloaded).

If you don't have a full backup, you're taking unnecessary risks with your data.