# supply more power trough usb ports  [UNSOLVED]

## theme

Hi,

I have an external Lacie hdd which is compatible with usb 2.0, and fireware. My problem is that when I connect it to my PC the led turns on but the system does not recognize it. I need another usb-to-power cord to connect the supply port of the external hdd to another usb port to get it working and for system to recognize it. 

My PC has usb 2.0 support:

```

angel@mine:~/Documentos$ lspci

<output omitted>

00:1d.0 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #1 (rev 01)

00:1d.1 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #2 (rev 01)

00:1d.2 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #3 (rev 01)

00:1d.3 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #4 (rev 01)

00:1d.7 USB Controller: Intel Corporation 82801G (ICH7 Family) USB2 EHCI Controller (rev 01)

<output omitted>

angel@mine:~/Documentos$ 

```

Are this power supply solutions required in usb 1.0 also necessary in usb 2.0? I thought that it was solved in usb 2.0 and only connecting one usb cord would be sufficient. Am I wrong?

thanks.Last edited by theme on Wed May 06, 2009 9:15 am; edited 1 time in total

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## MaximeG

Hi,

I have an external HDD (Western Digital though) in USB 2 and requires an additional power supply wire as well.

USB2 just grants you more speed but not more power imho.

Regards,

Maxime

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## theme

thanks MaximeG,

 it seems to be true, in this link

http://en.wikipedia.org/wiki/USB#Power

in section power they say that external hdds might not follow the standard power requirements and thus an additional power supply cord is needed. I think that this is because the PC does not supply more energy than the especified by the standard through a single usb port.

So now i change my question and thus the topic. Is there any way trough configuration to let the PC supply more power trough usb ports?

thanks.

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## monsm

 *theme wrote:*   

> 
> 
> So now i change my question and thus the topic. Is there any way trough configuration to let the PC supply more power trough usb ports?
> 
> thanks.

 

Short answer: No.

Far as I know, you might be able to reduce power to as USB device.  I think windows have such an option. I don't think thats enabled in the Linux kernel though.  I think if a USB device is plugged in, it has access to the maximum already.  Have a look here:

http://www.gentoo.org/doc/en/power-management-guide.xml#doc_chap6

Mons

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## hoacker

A Y-connector cable may be a solution (got an external drive with that cable). With that cable you can use the power supply of two USB ports.

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## eccerr0r

 *theme wrote:*   

> So now i change my question and thus the topic. Is there any way trough configuration to let the PC supply more power trough usb ports?

 

No.  Most USB ports' power rails, in order to save on costs, are simply hooked straight up to the power supply (possibly through a poly (self resetting) fuse).  There's usually no software configuration of power.

This isn't such a big deal as supposedly devices should use power they need.  However I found for the most part, USB mechanical 2.5" hard drives tend to use much more power than many USB ports can supply.   Hard drives tend to consume quite a bit of power getting the spindle up to speed.

I've found only a handful of laptops and desktops able to power a USB external 2.5" HDD normally.  If it can't do it, likely it will never be able to do it.  The poly fuse, which is normally a protection device, also adds additional resistance into the circuit, limiting power available to disks, also making it difficult to spin.

I suspect the "cheap" method of straight wire (no fuse) or traditional fuse (that can be a pain to replace) versus using the more expensive poly fuses may allow hard disks to spin up.  I've seen most hard drives use up to 500mA on the 5V line which is exactly the limit of USB, so it's no surprise there's a lot of marginals out there.  Best bet is to get some external power method for the HDD.  Yes, it defeats the purpose of having no power brick, but these 2.5" disks weren't meant for it anyway...

The Y-cable helps sometimes, as it ends up putting two of the poly-fuses in parallel, thus decreasing the resistance to the power source and possibly allowing enough clean power to reach the hard drive.  I've had some computers fail that even, so YMMV.

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## Plague.CZ

Why don't you set it as solved? The solution is: no. If you don't trust wiki, then see the official docs http://www.usb.org/developers/docs/. Where they state the maximum 500mA current. As from my experience, the Y-cable does work, just make sure to stick it into independendent USB slots (mostly there are 4 - 2+2 sockets in the back of your PC, so use one from each couple).

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## think4urs11

 *Plague.CZ wrote:*   

> As from my experience, the Y-cable does work, just make sure to stick it into independendent USB slots

 which is in some cases no option as the two usb slots might be to far apart from each other to use a standard-sized Y-cable.

The only option to (offically) get more power out of an USB slot than 500mA is to wait for USBv3 - new maximum 900mA iirc.

Annother option is to use a powered USB hub; some of them allow more than .5A per slot.

Lastely ... change the enclosure of the drive can be enough; did just that - throwed away a iomega enclosure, using a noname one now and the former iomega-HD works by miracle without Y-voodoo  :Smile: 

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