USB slow when two devices connected

[Phil Meyer]

Aldo Foot wrote:
> My F8 system has two USB ports in the front side.
> I had a USB DVDRW connected to one of the ports and was writing an ISO
> image to CDR.
> Then I plugged in a USB stick to transfer some files from it to my
> desktop, the transfer
> was stalling and was slow even after the CDR task ended. Then I
> unplugged the DVDRW
> and the USB stick transfer rate was as fast as lightning.
> Why was the USB stick file transfer so slow when the DVDRW was plugged in?
>
> ~af
>
>   

Most modern mother boards offer as many as 8 USB ports on as many as 4 
different USB controllers.  However, there are many motherboards that 
offer only 4 total USB ports on a single controller.

lsusb is useful to determine what's what in your particular system.

# yum install usbutils

if you need to.

All that, to say this:  a single slow USB device on a controller will 
cause the controller to drop to slow (USB 1.1) mode.   Not just a single 
port drops, the whole controller drops.

Plug both devices in at the same time and check lsusb output.  Are they 
both on the same controller.  Check dmesg output.  Did the USB driver 
complain about a 'slow' USB device?

Again, using lsusb, it is possible to plug in the second device in a 
different slot, and have it show up on a different USB controller.

On my laptop (newish) the two ports on the side are together, and the 
two on the back are together on a different controller.  Many laptops 
use at least one USB controller for internal connections.  Mine has an 
internal Bluetooth, and sits on a USB controller.

This problem used to be very problematic when most USB mice and 
keyboards were USB 1.1

Now days, all USB devices should say 2.0 on them somewhere.

Here is a sample output from lsusb:
 -> lsusb
Bus 002 Device 006: ID 1307:0163 Transcend Information, Inc. 512MB USB 
Flash Drive
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 009: ID 046d:c03f Logitech, Inc. UltraX Optical Mouse
Bus 006 Device 008: ID 050d:0109 Belkin Components F5U109/F5U409 PDA Adapter
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 003: ID 051d:0002 American Power Conversion 
Uninterruptible Power Supply
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 005: ID 0a5c:4503 Broadcom Corp.
Bus 003 Device 004: ID 0a5c:4502 Broadcom Corp.
Bus 003 Device 003: ID 413c:8126 Dell Computer Corp. Wireless 355 Bluetooth
Bus 003 Device 002: ID 0a5c:4500 Broadcom Corp.
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

The thumb drive and APC are on the side of my laptop on different 
controllers.
The Belkin USB serial device and the Logitech mouse are plugged into the 
back, and are on the same controller.  Your Mileage will vary.

When my mouse plugs in, dmesg says this:
usb 6-2: new low speed USB device using uhci_hcd and address 9
usb 6-2: configuration #1 chosen from 1 choice
input: Logitech USB-PS/2 Optical Mouse as 
/devices/pci0000:00/0000:00:1d.1/usb6/6-2/6-2:1.0/input/input18
input,hidraw0: USB HID v1.10 Mouse [Logitech USB-PS/2 Optical Mouse] on 
usb-0000:00:1d.1-2

Please note the words/phrases LOW SPEED and 1.1.  If I plugged my thumb 
drive into the back at the same time my mouse was plugged in, in the 
back, transfers would drop to about 1MB/sec.

Good Luck!