external hard drives

[Ronald Foltz]

i have a Dell Optiplex 280, Windows XP Pro system 32
250 GB HD w/197 GB available
2 GB RAM w/1.96 GB available. .
my problem is, i have two Maxtor external hard drives, one is powered by an
ac cord and the other by usb. . both will not operate at the same time. . if
one (or the other) is plugged in, i will get the message "external usb
device not recognized" when i plug the other one in. .
any info greatly appreciated thanks Gene

 

[R. McCarty]

Attempting to run both simultaneously exceeds the maximum
current draw of the USB Root Hub. 500mA ( one-hall Ampere ).
Likely both are USB-2 type devices and your PC only has a
single USB 2 Controller/Hub. Either the USB powered device
needs it's own DC supply or you'll have to install a separate USB
controller card to host the unpowered device. Some USB drives
(2.5" style) derive their power from the +5Volts of the bus itself.

 

[Patrick Keenan]

i have a Dell Optiplex 280, Windows XP Pro system 32
250 GB HD w/197 GB available
2 GB RAM w/1.96 GB available. .
my problem is, i have two Maxtor external hard drives, one is powered by
an ac cord and the other by usb. . both will not operate at the same time.
. if one (or the other) is plugged in, i will get the message "external
usb device not recognized" when i plug the other one in. .
any info greatly appreciated thanks Gene

Hard disks generally draw an amp or more - look on the disk label for the
precise current draw.

USB ports supply a maximum of half an amp.

So, it's most likely that you are simply exceeding the current draw for the
port, or hub.

USB-powered hard disks normally come with a 3-headed cable so that you can
draw power from two ports at once. However, it's still possible for you to
have enough devices on the root hub to be exceeding the maximum current.

HTH
-pk

 

[Twayne]

Attempting to run both simultaneously exceeds the maximum
current draw of the USB Root Hub. 500mA ( one-hall Ampere ).
Likely both are USB-2 type devices and your PC only has a
single USB 2 Controller/Hub. Either the USB powered device
needs it's own DC supply or you'll have to install a separate USB
controller card to host the unpowered device. Some USB drives
(2.5" style) derive their power from the +5Volts of the bus itself.

Doesn't seem like that should be it? He said one of them is powered by
an external ac connection so only one is getting its power from the USB
port?
Actually, he didn't say they were USB2 ports either, now I think
about it. I wonder how old the Optiplex is?
It almost sounds like the two are contending for the same resources;
a check of the Properties might be in order or exchanging one USB port
for another.

Just my 2 curious ¢.
Twayne