A31 USB Power

[rnfolsom]

My wife has a "desktop computer replacement" IBM Thinkpad A31-C4U-2652 (which which she is delighted) running Win2k Sp4 (which provides USB 2.0 support), and we are planning on using some USB devices with it. These devices may require USB power (rather than use an external AC power supply), but would be used only when the computer itself is using ACPower (vice battery only power).

Because the A31 USB ports are 1.1 (vice 2.0), we probably will want to get a Cardbus card that provides USB 2.0 connections.

My questions are

1) How much power (e.g. milliamps) do each of the original USB 1.1 ports provide?

2) How much power would a USB port on a Cardbus card provide?

3) I'd be interested in any recommendations of any Cardbus USB port cards.

For my first two questions, of course I would like precise answers <grin>, but since I don't have any clue at all, I'd appreciate not only precise answers but also guesstimates.

I checked the Tawbook, and also ThinkWiki, but I was not able to find this information there.

I know I am being "coy" by not saying what devices I have in mind, but for now I'd like to focus attention on those specific "how much power" and cardbus USB questions.

I'll explain more precisely what the devices are in a later post in this thread.

Thanks for any help.

Cordially, R.N. (Roger) Folsom

[ElbertR]

1) According to the Win XP Device Manager 500mA per port

2) Most likely 500mA per port (this seems to be the standard for all ports).

3) Plenty of good ones around. 2 or 4 ports, some even have an extra power connection. Just do some shopping around.

[LtTPfan]

I just ordered a USB 2.0 PCMCIA card and the specs on it said:

* Total 5V/500mA Bus Power Shared by 2 USB Devices.
* Current Protection Active lf Bus Power Over 500mA.

I just read the specs for a different brand of 4-port card and it said the same thing but shared by 4 USB devices.

[FuguTabetai]

I've got a ThinkPad A31 2562-D4U (very happy with it) and have recently purchased a cardbus 2 USB2 / 2 FireWire port card. (Q-stor brand, works very well with Win XPSP2 and more importantly linux, although the latest Fedora Core 4 kernel has some isssues that a kernel downgrade fixes...)

The firewire and USB ports are not powered by the A31. The card includes an input for an external power supply to power the ports.

I've already read somewhere else on this forum that USB ports on PC cards haven't been powered.

This could depend on the USB card, but my guess would be that in general the A31 doesn't provide that much current to the PCMCIA slot.

Hope that helps (but probably just throws more confusion on the subject.)

[cpn]

I am using the Apricorn EZ USB 2.0 card and it provides the full amount of power to the USB without using an external power adapter. The bad news, it uses a dongle instead of a fixed extension. The good news is it uses a dongle instead of a fixed extension and I can use more then one PC card now in my laptop.

Craig.

[rnfolsom]

I am using the Apricorn EZ USB 2.0 card and it provides the full amount of power to the USB without using an external power adapter. The bad news, it uses a dongle instead of a fixed extension. The good news is it uses a dongle instead of a fixed extension and I can use more then one PC card now in my laptop. Craig.

My initial message that started this thread promised to explain why I was asking about the A31's USB power outputs. The answers here have all been helpful, and thanks to everyone who contributed. I have not had definitive information of my own to contribute until this week.

Like Craig (cpn), I have acquired an Apricorn Ez USB2 CB Cardbus PCCard-with-dongle. The dongle has two USB 2.0 ports: the top one can supply 500 milliamps, but the lower one only 100 milliamps (as marked on the side of the dongle). My focus in this thread is on my wife's IBM Thinkpad A31, but I know that on a Dell C840 laptop (and likely other Dell "desktop replacement" laptops), each Cardbus slot can supply 1 amp max (2 amps total for both slots running simultaneously), and since a Cardbus card itself uses some power, it makes sense that one Cardbus USB card could not provide 500 milliamps to both of its USB ports simultaneously.

Apricorn's description of its Ez USB2 CB cardbus card is at
http://www.apricorn.com/product_details.php?ID=314

I acquired the Apricorn Ez USB2 Cardbus PCCard-with-dongle to use with an Apricorn EzBus 80gb 2.5" portable external hard drive, which accepts either USB 2.0 or 1.1 data, and gets its power from two USB ports. According to Apricorn's post-purchase voice tech support, the drive needs 750 milliamps = 0.75 amps. (I'm using the drive for backups, and a major attraction is that it is physically small enough to fit into a bank safe deposit box.)

Apricorn's description of its Ez Bus 80gb external drive is at
http://www.apricorn.com/product_details.php?ID=330

Apricorn's pre-sales website documentation (and also the user manual that accompanied the drive, which refers to a wrongly named "AC Adapter to USB" cable) led me to believe that this drive could use, as an option, an external power supply, but when it came there was no external power supply, and Apricorn's post-purchase voice tech support tells me no external power supply is available.

Instead, the external drive comes with two USB cables:

1) A supplementary power cable connects one of the computer's original USB ports to a power input port on the external drive, and

2) A data cable connects one of the computer's original USB ports, OR the Ez USB2 Cardbus 500ma port, to the external drive's USB-Mini-B port. This data cable not only transmits data between the computer and the external drive, but also supplies power to the external drive.

Presumably, the drive would work with a different Cardbus USB port, provided it provided 500ma (or at least 250ma, if the supplementary original USB port provides 500ma, given that the drive needs 750ma).

Unless the computer is shut down, the two cables should be connected in the order I have stated (according to the drive User Manual, FAQ5 on page 25): supplementary power, then data. Taken together, the two USB ports are supposed to supply adequate power to the drive.

And in my experience, they do so, not only on my wife's A31, but also on my Dell Latitude C800 and C840 computers. I have tested by backing up and restoring each computer's partition images, using the computer's two original USB 1.1 ports, or using one original USB 1.1 port and the Ez USB2 Cardbus 500 milliamp port. Everything worked with no problems. For actual use, obviously I would prefer the second setup due to USB 2.0's much faster speed.

I had no reason to try bypassing both original USB 1.1 ports, and instead using two USB 2.0 500 milliamp ports, one on each of two Ez USB2 Cardbus cards running simultaneously. But I suspect that would work --- at least on my Dell laptops, since each of their Cardbus slots can provide 1 amp (some of which the card itself uses) even when running simultaneously. However, given that either of the original USB 1.1 ports apparently can provide 500 milliamps (even when running simultaneously, at least on the Dell), there is no reason to use a Cardbus USB port to supply that supplementary power.

Apricorn voice technical support assured me not only that this USB-powered external drive should work with "any" laptop using two cables and power from two USB ports as described above, but also that for some laptops (he could not provide any examples), the supplementary power cable is not necessary: only the data cable is needed, because the computer has a USB port that can supply the drive's needed 750 milliamps. But with each of my three computers, both cables were necessary. I suspect that to use only one USB port and one cable, a necessary condition might be that the one USB port be USB 2.0 vice 1.1, or that the computer be a desktop rather than a laptop.

Apparently, trying a "one USB port and one cable" experiment does not damage either the computer or the drive. Apricorn and Dell both say that computers (and Apricorn's USB2 card) have "current limiting circuits" (Dell's wording). In my own "one USB port and one cable" experiments, all failures, Windows Explorer (in Windows 2000) simply would not "see" the drive. And at least sometimes (perhaps always; my notes on that are sloppy), there was an error message.

Roger Folsom