Why so weak?

Michael73

macrumors 65816
Original poster
Feb 27, 2007
1,078
33
I have a wired Apple keyboard (the kind with a number pad)...it's a couple of years old but that shouldn't matter. The keyboard is plugged into one of the USB ports on my 30" ACD. How come when I plug in a single USB2 thumb drive into either of the two USB ports on the bottom of the keyboard it says "USB Device Needs Power. Connect "USB 2.0 FD" to power or a USB port on this Mac."

Does a thumb drive really require that much power?!? I realize it's daisy chained but both of my USB ports on the ACD are used (one for the keyboard, the other for a docking cord for my iPhone) and all four USB ports on my nMP are in use.

I'm pretty sure my neighbor who has an iMac and a wired keyboard has no problem using the USB ports on the keyboard for his thumb drive. Does the iMac USB ports provide that much more power?!?
 

FreakinEurekan

macrumors 68040
Sep 8, 2011
3,391
329
Eureka Springs, Arkansas
I'm pretty sure my neighbor who has an iMac and a wired keyboard has no problem using the USB ports on the keyboard for his thumb drive. Does the iMac USB ports provide that much more power?!?
Sort of. From http://support.apple.com/kb/ht4049 :

*When connected to a computer that supports a connection of 1100 mA at 5 V, the first port on the keyboard to have a device or peripheral connected to it that requests standard 500mA power will receive that power. At that point, 100 mA at 5 V is available through the remaining port on this keyboard. This keyboard does not support extra power out of its two ports simultaneously; it requests extra power from the host computer to provide power out of either one of its two ports, then the second keyboard port receives the standard 500mA.
 

Altemose

macrumors G3
Mar 26, 2013
9,089
444
Elkton, Maryland
I have a wired Apple keyboard (the kind with a number pad)...it's a couple of years old but that shouldn't matter. The keyboard is plugged into one of the USB ports on my 30" ACD. How come when I plug in a single USB2 thumb drive into either of the two USB ports on the bottom of the keyboard it says "USB Device Needs Power. Connect "USB 2.0 FD" to power or a USB port on this Mac."

Does a thumb drive really require that much power?!? I realize it's daisy chained but both of my USB ports on the ACD are used (one for the keyboard, the other for a docking cord for my iPhone) and all four USB ports on my nMP are in use.

I'm pretty sure my neighbor who has an iMac and a wired keyboard has no problem using the USB ports on the keyboard for his thumb drive. Does the iMac USB ports provide that much more power?!?
In all fairness, these USB power limitations have been around since they moved away from ADC in my experience. Another thing to note is that my PNY drives work just fine on my wired keyboard, but if I plug in a SanDisk CRUZER USB flash drive I get warnings everywhere about power.

Some flash drives are power pigs. One thing you need to understand is that a USB port puts out 500 mA of power. That power is split amongst the keyboard and whatever is plugged into it whether it be a mouse or whatever. All USB ports on any modern computer are going to individually put out 500 mA even if on the same controller.

Try plugging to USB power pigs into a PCI PowerMac G4 and see what happens :D. I recommend getting a powered USB hub to attach to the port on you monitor.