Some USB ports 2.0, others not?

  • Thread starter Thread starter Richard Carpenter
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Richard Carpenter

I have a Shuttle XPC, and it has USB ports on both the front and the
back. However, only those on the back are USB 2.0 for some reason. The
ports on the front won't adequately power my external hard drive and my
ATI USB 2.0 video capture device failed to work on the front, while
working just fine on the back.

The front ports work fine for things like an external floppy drive,
mouse and USB thumbdrive, just not with devices that require USB 2.0.

Is it possible that a seperate USB controller is used for the front
ports than the back? If so, why would the manufacturer have used USB
2.0 only on the rear ports? Anyone else have any experience with that
sort of thing?
 
Richard said:
I have a Shuttle XPC, and it has USB ports on both the front and the
back. However, only those on the back are USB 2.0 for some reason. The
ports on the front won't adequately power my external hard drive and my
ATI USB 2.0 video capture device failed to work on the front, while
working just fine on the back.

The front ports work fine for things like an external floppy drive,
mouse and USB thumbdrive, just not with devices that require USB 2.0.

Is it possible that a seperate USB controller is used for the front
ports than the back? If so, why would the manufacturer have used USB
2.0 only on the rear ports? Anyone else have any experience with that
sort of thing?
Click to expand...

There was a short interval in time, where the main motherboard chipset
(the Southbridge) might have had USB 1.1 ports. To supplement the ports,
a manufacturer could add a separate USB2 chip, sitting on the PCI bus.
The computer then ends up with some ports which are USB 1.1 only, and
other ports which are USB2.0/USB1.1 capable.

Motherboards shipping now, can have 8-10 USB2 ports, all supported
by the Southbridge. On modern motherboards, there is no need to
supplement the design, with a separate chip.

One reason for ports to fall back to USB 1.1, is electrical signal
quality. USB 2.0 needs good transmission line quality to work. If
you had "loose wires" somewhere in a cable assembly, the impedance
of a wire sitting loose in the air, is uncontrolled. That is enough
to upset a high speed signal. Also, some computer case front panel
assemblies, seem to have EMI filters on them, which can disrupt USB2
operation.

When you talk of power, the max power that a USB 1.1 or a USB 2.0 port
can deliver is 5V @ 500mA. That is not enough to spin a disk drive,
whether the disk is 2.5" (notebook) or 3.5" (desktop) sized. To spin
a 2.5" disk, some enclosure products come with two USB connectors. When
both USB connectors are connected, then you can get 5V @ 1 amp, which
is enough to spin a notebook drive. But the power consumption of
3.5" 7200RPM drives, is 12 or 13W at idle, and 12V @ 2A is needed during
the 10 second spinup interval. Such a power load typically requires
an external adapter. There are some Firewire enclosures, that "save
up power", in order to get enough to spin up a 3.5" drive. But personally,
if using a drive, I'd prefer to see a steady reliable source of spindle
power, in the form of an AC adapter.

Paul
 
Paul said:
< snip >

When you talk of power, the max power that a USB 1.1 or a USB 2.0 port
can deliver is 5V @ 500mA. That is not enough to spin a disk drive,
whether the disk is 2.5" (notebook) or 3.5" (desktop) sized. To spin
a 2.5" disk, some enclosure products come with two USB connectors. When
both USB connectors are connected, then you can get 5V @ 1 amp, which
is enough to spin a notebook drive. But the power consumption of
3.5" 7200RPM drives, is 12 or 13W at idle, and 12V @ 2A is needed during
the 10 second spinup interval. Such a power load typically requires
an external adapter. There are some Firewire enclosures, that "save
up power", in order to get enough to spin up a 3.5" drive. But personally,
if using a drive, I'd prefer to see a steady reliable source of spindle
power, in the form of an AC adapter.
Click to expand...

You are correct there. My external HDD is a 2.5", and it utilizes two
USB connectors at once.
 
I also have this same problem with my Shuttle XPC. I went back to the
shuttle website and it does say that I should have 4 USB2's at the back
and 2 USB2's at the front.

Have you found out anymore since you posted this
 
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