USB display adapters for multiple monitors and USB hub?
I bought one of those USB-DVI/HDMI adapters for plugging more than one external monitor to my notebook.
I also bought one of those "el cheapo" USB hubs, to allow more monitors using the same usb port, but if I plug the adapter through this hub, the screen performance drops considerably. Lags start showing up and such. Even if only one adapter. Remove the hub and plug the adapter directly to the native usb port, all set. No lag, good performance for charting (no notable difference from the native HDMI port).
Has anyone also ran into the same problem? Is anyone else also running this kind of setup (usb display adapters from a single usb port via a usb hub)?
There are more expensive (and bulky) USB hubs with external power supplies, maybe these will work as the "native" ports?
i have used a single display adapter using usb 2.0 to run a 24" monitor and has worked for 7+ years... I'm thinking of getting a new computer and will use single adapters for extra monitors using 3.0 usb ports. i haven't used one of those multi display adapters so can't comment on them.
Actually, the usb display adapter I'm using is the type that requires one per extra monitor. So to use two external monitors, I need two separate adapters plugged into their own, separate, usb ports. That's where the usb hub comes in handy.
You will always run into the speed issue with these type of USB hubs. Each USB port can only handle so much I/O bandwidth and I believe a 1080p display is either close to, or already exceeds, the ideal bandwidth needed to have a non-stuttering or smooth refresh of your display. Once you try and do this via a hub, you end up trying to double the data throughput while still having the same limitation of your USB port.
I noticed that the display adapter is USB 2.0. If you can get one that is USB 3.0 or more preferably 3.1 or Thunderbolt, then it may lead to a decent increase in speed. I never tried this though, so you would need to do your own research.
A much better solution to this would be to have a PC with the appropriate number of GPUs in there. No need to go overboard with the horsepower, any cheap cards will do as long as they have the correct number of display output options. Refer to this link for some examples of better GPUs - https://futures.io/tech-support/36228-pc-build-trading.html. These GPUs can handle a fair number of displays.
If you want to use a laptop your options become somewhat more limited - Alienware Graphics Amplifier | Dell. This will work with an Alienware laptop, but you can only use one of these boxes per laptop. Thus, need to pick a GPU that leaves you with the desired number of displays.
Or, you could just get 2 laptops and hook up one external display to each (to either your VGA / HDMI, etc). Gives you some redundancy and reduces the headaches associated with the USB-adapters.
Edit: The external Dell housing may only work with Alienware laptops - Don't buy the housing and expect it to work unless your laptop is compatible.
Last edited by grausch; August 17th, 2015 at 04:13 AM.
Reason: Added missing data
The following user says Thank You to grausch for this post:
Thanks a lot for the insights! The thing is that the litlle adapter works great if plugged directly to notebook usb port. No lags, crisp image, for charting, no notable difference from the monitor plugged in the native hdmi port.
The lags appear when using the "el cheapo" usb hub (which is supposed to be 2.0 spec). Even when I plug said hub to the usb 3.0 port on the notebook and there is only one adapter plugged in the hub with all other it's ports empty (so there shouldn't be any bottlenecks there, but it seems I'm wrong).
Would a USB 3.0 hub work better? I'm looking to plug up to 3 extra monitors (so, 3 adapters).
That's really odd - I always thought you would still get the full bandwidth to and from the USB port even with a USB hub. For instance, plugging in just the screen with the adapter should not lead to any difference in performance. Should be noted though, that while I am very comfortable with PCs, I am completely unsure as to how a USB hub splits the lanes. I know of a couple of ways this can be done in theory, but have never opened one up in real life. The cheapest way would literally be to divide the lanes between each port of the hub, i.e. a 4 port hub will have each port running at 1/4 speed. Not sure if this is feasible or if manufacturers actually do this. However, I always thought there is a chipset inside the hub controlling the data ensuring that you still get close to your maximum bandwidth.
Will you see an increase in speed if you use a USB 3.0 hub? Yes, definitely. The fact that your adapters are USB 2.0 should not influence the speeds going to and from the hub to the PC. Will you be able to run 3 extra monitors? I don't know, but I doubt it - don't think USB 3.0 can handle that amount of data.
I was wrong about the speed improvements with a USB 3.0 hub - your USB 2.0 devices will not have access to the USB 3.0 total bandwith (5 Gbps) that I expected. You will need to share the USB 2.0 bandwdith (480 Mbps) and that will surely be inadequate for 3 displays.
Last edited by grausch; August 17th, 2015 at 09:45 AM.
Reason: Major error correction
The following user says Thank You to grausch for this post:
Although I do have a decent grasp of the software side, hardware is not really my forte. Still lots to learn. Thanks for the wikipedia link on USB hubs! Lots of helpful info there.
The problem seems to be the hub itself. I believe the notebook does have more than enough horsepower to drive the adapters, specially for charting (where only a small fraction of the screen changes at every tick). The CPU is a 2.4GHz i7, it's got 16GB RAM and a pretty decent 2GB dedicated video card (Radeon M295 if I remember correctly). As I said, the adapters work just fine if connected to the usb ports on the notebook itself.
After you mentioned that some USB hubs share the same lane across all ports, I began suspecting that was the case with this hub I have. The wikipedia link "sealed it". Disassembling the hub to look at it's circuitry, what I found is in the attached pictures.
Seems like you really get what you pay for...
The following user says Thank You to AMGT for this post:
Yes, it looks that way. Didn't think they would actually build them that way, but it was the only explanation that made sense. You can of course test this copying a large file across an external drive, first via the hub and then via your USB port on the notebook.
I'll admit that I don't know a lot about these USB adapters - I was looking at one a couple of years ago (maybe 2006 or 2007) and every time the screen refreshed, you could see it quite clearly. Haven't look at them since due to that. What I don't know how the USB adapters process the data, i.e. does it use the CPU or the GPU or does it do computations on the adapter itself? The aforementioned link to the Startech adapter let's me think that it uses the GPU (or iGPU if available) and that would be the best-case scenario. However, you are planning on pushing a lot more pixels than the GPU was designed for. Since you won't be gaming it may work - there is no difference between a GTX 980 and my Intel HD 3000 when I run Microsoft Office.
In order to satisfy my curiosity, would you please post some updates as and when you get the relevant hub, adapters and screens? Really curious to see whether this will work. If it does not work, just get a second notebook and you can still hook up all of your displays.
Edit: You could also look at Thunderbolt or USB 3.1 - their bandwidth may actually get this to work, but again, no clue whether there are any adapters for that available and whether your GPU will be able to handle that.
Last edited by grausch; August 17th, 2015 at 11:10 AM.
Reason: Thunderbolt / USB 3.1