high and low powered USB ports

[savarin]

I have several Thinkpads and have always problem when I want to buy a peripheral connected via USB.

I do not know USB 2.0, but USB ports 1.1 were divided in high powered (c. 500 mA) and low powered (c. 250 mA and less). It is very useful to know which port is on your machine when you want to buy for instance a modem without external power. In such a case a high powered USB port is mostly enough.

I can not find any documentation about Thinkpads USB ports. I do not mean information about number of ports or about USB version. I look for practical, useful info saying - Thinkpad XXX has 1 highpowered USB port on the right side and 1 lowpowered USB port on the left side.

Do you know these informations? Could anybody help?
Thank you.

[RBob]

Do you know these informations? Could anybody help?

This isn't a direct answer to your question, but (assuming you're running Windows) if you go to the Windows "Device Manager" and look at the properties of the USB hub(s), you'll find a tab labeled "Power" which claims to show the current handling capacity of each port.

Also, if any peripherals are currently plugged into a port, it shows how much current that peripheral is using.

I don't know if those numbers are accurate.

[Ken Fox]

I have several Thinkpads and have always problem when I want to buy a peripheral connected via USB.

I do not know USB 2.0, but USB ports 1.1 were divided in high powered (c. 500 mA) and low powered (c. 250 mA and less). It is very useful to know which port is on your machine when you want to buy for instance a modem without external power. In such a case a high powered USB port is mostly enough.

I can not find any documentation about Thinkpads USB ports. I do not mean information about number of ports or about USB version. I look for practical, useful info saying - Thinkpad XXX has 1 highpowered USB port on the right side and 1 lowpowered USB port on the left side.

Do you know these informations? Could anybody help?
Thank you.

I believe that MOST of the USB ports on Thinkpads, at least ones made in the last few years, are high powered, EXCEPT that the X30/X31/X32 had a low powered left side port and a high powered rear port. I don't know what they did with the X40/X41 series, but to my knowledge all the X6x/R6x/T6x/Z6x machines have only high powered ports.

The situation with the X3x was a compromise given the small size and limited battery power of the system, and was not typical of other Thinkpads. At the time the X3x series chassis first came out, USB ports were not ubiquitous on laptops, and it was not uncommon to find ONE USB port or no USB ports on notebooks.

I don't know what the actual definition of "high power" is in this situation but I take it to mean that the port can put out enough power to run a hard drive. Lower power requirements, such as for reading a flash memory item or running a floppy, can be powered by a low power port.

Optical drives, even small form factor (half height) drives meant for use with laptops, generally have their own power sources and to my knowledge there are few or no available ones that can run solely off of USB bus power.

There are a bunch of silly accessories that are marketed to run off of USB power, stuff like fans and accessory lights and coffee cup warmers. I'd avoid those gimmicks like the plague, whether or not it can theoretically be powered by the laptop or not.

[bill bolton]

I do not know USB 2.0, but USB ports 1.1 were divided in high powered (c. 500 mA)

Without going too far into the detail, basically USB 2.0 specifies compliant ports as having a low power (!~100mA) and a high power (~500mA) mode which is negotiated with the connecting device.

As far as I am aware, the ThinkPad USB 2.0 ports are fully compliant as far as power mahagement capability goes, but a lot of other USB equipment, particular items which basically only draw power from a USB port, are not, in that they have no power negotiation capability.

Cheers,

Bill

[pjk]

Optical drives, even small form factor (half height) drives meant for use with laptops, generally have their own power sources and to my knowledge there are few or no available ones that can run solely off of USB bus power.

Plextor now has a DVDRW drive that can be either external or bus-powered:

http://www.plextor.com/english/products/px-608cu.html

There are a bunch of silly accessories that are marketed to run off of USB power, stuff like fans and accessory lights and coffee cup warmers. I'd avoid those gimmicks like the plague, whether or not it can theoretically be powered by the laptop or not.

Someone else said that the ports negotiate with the device whether it wants "low" or "high" power. And while I agree that A) these sorts of devices are almost certainly "dumb" and thus cannot engage in this negotiation, and B) some of them probably violate the 500 mA maximum anyway (especially things with heating devices.. yikes!) nevertheless I must admit there are a lot of very fun-looking USB toys I've seen that I'd love to play with..

[junglemike]

the actual numbers are usually far from the standards.
For example I am an engineer, and I've taken from my destop's Usb 1.5Amps w/ no problem. I also have a portable case with 2.5" hard drive which eats 1.1amps (at spin-up) and it works perfectly with T21 single usb1.1 port.
I once triggered a protection usb shutdown on some Toshiba laptop (by trying to consume too large current (>2Amps) Usb port disappeared in device manager and didn't work, until i restarted windows