How much power IS supplied by an X4* powered usb port?

[brainpicker]

I spent an hour looking for this answer and I can't find it so I'll ask here. Exactly how much power is supplied through the "powered USB 2.0 port" of an X40 or X41? I can't find anything through support other than various articles and papers stating the existance of this powered port. The USB spec states that a powered design must provide at least 4.5-V (at a current of at least 500mA), but since there is no maximum spec and designs are all over the place (with as much as 3A current) I need to know for sure what spec IBM/Lenovo used in the design of this port.

Here's why I'm interested. I have a nice compact CD-RW/DVD USB unit that operates on 5-V (at 2A) when powered through a tiny little a/c adapter. I was able to locate a USB "power" cable that terminates properly at the device end, but I don't want to risk damage to either the device or the laptop by trying this without knowing for sure that it won't be a risk. I know IBM makes several USB products that are "bus powered" and also supplies a special USB cable that's kind of a Y-adapter to draw power out of 2 USB ports should neither be a powered port. So I'm assuming this IS possible with my device even though it was not specifically designed to draw power this way, but I know next to nothing about electronics and power requirements. I do understand from reading that there is no real regulation of the power coming from a USB port and voltage fluctuation is very common because of this lack of regulation and wide variances in design from manufacturer to manufacturer (which is why it is possible, though not recommended, to charge say a mobile phone's lithium battery through a USB port... there is a chance of too much on-and-off charging or switching taking place), so my fear (or hope?) is that IBM has chosen a superior high-power design for theirs, maybe at a much higher voltage than the norm. For my use I suppose underpowering the device would not be destructive, but overpowering might. But then I remember reading somewhere in my past that it's not the voltage that matters but that too much current is what can cause the damage. If that is the case then it should be safe for me to at least try it... right? If I haven't already confused the hell out of you I sure have for myself!

Yep, this is why I'm the "brainpicker"!

Help?

[blackomegax]

if the current is coming and going to the right places, with the right voltage, it will work.

[snife]

I don't think it would cause any harm to try it but as far as I am aware you will not get any more than 1A out of the ThinkPad USB ports (500mA to each port is drawing on both).

[jw]

See http://www.usbpluspower.org -- I think this is what IBM/Lenovo is referring to.

PDF of specifications is here:
http://www.usbpluspower.org/specs/docum ... er_08f.pdf

Perhaps somebody with a X41 or X41 tablet can tell us -- it looks like the USB port on the left of the left side of the computer (by the fan) is just one dedicated "powered USB" port (twice as tall as a standard USB connector), with the other USB port on the right side. This contrasts with most of the reviews of the X41/X41T which states that there are 3 USB ports on this laptop, while the IBM/Lenovo website itself describes only USB ports.

If this truly is the specs, that means that this special port can support up to 6 amps, but uses a dedicated port. So unless you use the special connector you are not using the high-current capabilites of the port, and are instead just overtaxing a standard USB port (which could in theory overheat and burn out the IC power regulators).

The thing is I don't know how many devices are made using this connector--I don't really see many consumer devices using this connector, which may be why nobody knows what they are.