DisplayLink software resets with quad monitors

oldtopos · 07-13-2012, 05:13 PM

Running quad 1600x1200 monitors (plus laptop display) causes frequent software resets of displays. The resets can be triggered in some cases by simply dragging a window over all display surfaces.

System has been rebooted; usb cable to laptop unplugged and replugged several times.

Triple monitor configuration is stable, and has run without issues for several days.

Initial and post event traces are attached.

Carlo · 07-14-2012, 07:17 AM

I think it's a power problem. From the logs is seems that one adapter is sometimes falling off the bus, probably because it does not receive enough power, and then come back.
It looks like you have 4 adapters connected to a single hub. They are all nearly at maximum resolution so they're going to draw maximum current when something is moving on the screen. A standard 4 port hub power supply can't usually power more than 2/3 adapters in these conditions. A 7 port hub supply can usually power 3/4.
I'd move at least one adapter to a different hub or connect it directly to the computer, or buy a bigger power supply for the hub.

Carlo

oldtopos · 07-14-2012, 01:25 PM

Carlo,

Sounds plausible, as they are all connected to a single 10 port hub.

Early testing indicates better behavior with four monitors.

oldtopos · 07-17-2012, 03:19 PM

Carlo,

Moving one adapter off the USB hub did stabilize the system.

However, the hub is rated at 2.5 Amps, and this should be sufficient for four USB devices running at 500ma max. It's a 10 port Pluggable http://plugable.com/products/usb2-hub10s/

Are the adapters capable of drawing more than 500ma each ?

Carlo · 07-18-2012, 06:44 AM

Quote:

Originally Posted by oldtopos

Carlo,

Moving one adapter off the USB hub did stabilize the system.

However, the hub is rated at 2.5 Amps, and this should be sufficient for four USB devices running at 500ma max. It's a 10 port Pluggable http://plugable.com/products/usb2-hub10s/

Are the adapters capable of drawing more than 500ma each ?

We've seen adapters draw more than 500mA for high resolution digital connections yes. We've also seen some that are always below 500mA, but they tend to be much more expensive because the power circuitry is not cheap. Don't ask me the brand.
It usually depends on the electronics so it's a question for the device manufacturer really.

I any case when budgeting power for video adapters I'd consider them like external 2.5" HDs: up to 40% more than 500mA in peak conditions.
If you consider the power regulator efficiency inside the hub and other low power devices that might be connected you don't' have more than 3 adapters for a 2.5A power supply.

Carlo

KenSchisler · 10-25-2013, 01:28 PM

I am having the exactly same problem however I am not using a USB hub. I have the following:

Laptop Monitor
VGA montior plugged into my laptop
2 usb display ports plugged into my lap on different USB ports

my monitors reset 5-10 times a day (only the usb connected montiors shutdown and reset and all my applications go back to my main laptop monitor) and it drives me crazy as I have to reset the applications on my four screens everytime.

In reading this are you saying my laptop USB ports aren't delivering enough juice? How can I resolve this?

Thank you.

TheSnails · 10-31-2013, 03:53 AM

To Oldtopos and KenSchisler

I use 3 USB monitors based on displaylink with a 7 port USB hub by plugable. The power supply of the hub is 3A. On paper, 3A is more than enough to support 1.5 A (3 monitors x 500 mA). However, in practice, it is not. After several months, the power supply fails, and the monitors go awry (flickering, gray screen, etc.).

What I did was to get a 1A USB power adapter (the one that comes with iPod or iPhone) for each monitor. Each of the monitor comes with a Y USB cable. One end plugs to the hub, and one end plugs to the USB power adapter. Everything works fine now.

To Carlo

I tried to add a fourth USB monitor (the Lenovo LT1421) to my setup. I use a Macbook Pro with Mavericks OSX, and the 2.1 beta software. The setup with 3 monitors is fine, but when I add the fourth monitor, I experience similar issue as Oldtopos described. All 4 monitors are on, plugged to the same USB hub with 3A power supply, and each of them is plugged via Y USB cable to 1A USB power adapter. Although they are on, every time I arrange the monitors in OSX, I cannot see any of the window that I drag to the USB monitors. Small portions of the window is cut off on the screen, and I cannot manipulate any option available on the display settings that OSX shows in each USB monitor.

Could you help, please?

Thank you

07-14-2012, 07:17 AM	#2
Carlo Mac Team Join Date: Feb 2009 Posts: 606	I think it's a power problem. From the logs is seems that one adapter is sometimes falling off the bus, probably because it does not receive enough power, and then come back. It looks like you have 4 adapters connected to a single hub. They are all nearly at maximum resolution so they're going to draw maximum current when something is moving on the screen. A standard 4 port hub power supply can't usually power more than 2/3 adapters in these conditions. A 7 port hub supply can usually power 3/4. I'd move at least one adapter to a different hub or connect it directly to the computer, or buy a bigger power supply for the hub. Carlo

07-14-2012, 01:25 PM	#3
oldtopos Junior Member Join Date: Jul 2012 Posts: 5	Carlo, Sounds plausible, as they are all connected to a single 10 port hub. Early testing indicates better behavior with four monitors.

07-17-2012, 03:19 PM	#4
oldtopos Junior Member Join Date: Jul 2012 Posts: 5	Carlo, Moving one adapter off the USB hub did stabilize the system. However, the hub is rated at 2.5 Amps, and this should be sufficient for four USB devices running at 500ma max. It's a 10 port Pluggable http://plugable.com/products/usb2-hub10s/ Are the adapters capable of drawing more than 500ma each ?

10-25-2013, 01:28 PM	#6
KenSchisler Junior Member Join Date: Oct 2013 Posts: 1	I am having the exactly same problem however I am not using a USB hub. I have the following: Laptop Monitor VGA montior plugged into my laptop 2 usb display ports plugged into my lap on different USB ports my monitors reset 5-10 times a day (only the usb connected montiors shutdown and reset and all my applications go back to my main laptop monitor) and it drives me crazy as I have to reset the applications on my four screens everytime. In reading this are you saying my laptop USB ports aren't delivering enough juice? How can I resolve this? Thank you.

10-31-2013, 03:53 AM	#7
TheSnails Junior Member Join Date: Oct 2013 Posts: 5	To Oldtopos and KenSchisler I use 3 USB monitors based on displaylink with a 7 port USB hub by plugable. The power supply of the hub is 3A. On paper, 3A is more than enough to support 1.5 A (3 monitors x 500 mA). However, in practice, it is not. After several months, the power supply fails, and the monitors go awry (flickering, gray screen, etc.). What I did was to get a 1A USB power adapter (the one that comes with iPod or iPhone) for each monitor. Each of the monitor comes with a Y USB cable. One end plugs to the hub, and one end plugs to the USB power adapter. Everything works fine now. To Carlo I tried to add a fourth USB monitor (the Lenovo LT1421) to my setup. I use a Macbook Pro with Mavericks OSX, and the 2.1 beta software. The setup with 3 monitors is fine, but when I add the fourth monitor, I experience similar issue as Oldtopos described. All 4 monitors are on, plugged to the same USB hub with 3A power supply, and each of them is plugged via Y USB cable to 1A USB power adapter. Although they are on, every time I arrange the monitors in OSX, I cannot see any of the window that I drag to the USB monitors. Small portions of the window is cut off on the screen, and I cannot manipulate any option available on the display settings that OSX shows in each USB monitor. Could you help, please? Thank you