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For my new setup, my main prerequisite is three 1920*1200 monitors in portrait.

I would preferably want to use them with a laptop though, so it seems my options are:

  • Matrox TripleHead2Go
    But I don't really like the idea of having three monitors fused into one.

  • 3 dedicated USB->DVI adapters
    Here I'm worried that the USB bus will get clogged resulting in degraded performance, especially since I'll need to resort to a USB hub in any case, to plug other devices in.

This setup would be used for working mostly with text, no gaming, but it would be a bummer if performance was so bad it couldn't decently play a video.

Does anyone know what kind of performance can be expected from the USB adapters solution?

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Bare in mind that my experience with Multi-Monitor setups is limited, but if you do not want the Matrox TripleHead2Go because you're leery of fusing three monitors into one, in practice how would that be different than using your OS to stretch the desktop across them? –  Xantec Nov 2 '10 at 13:42
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4 Answers

You could probably get decent performance if you picked up an ExpressCard-to-USB adpater. Otherwise, I wouldn't try more than a single display via USB.

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USB 2 has a maximum theoretical throughput of 60MB/s, one monitor at 1920*1200 at, say, 24 bit (Let's assume the alpha channel is precomputed, it probably is) is 6.6MB, give or take a few decimal places. One monitor at a refresh rate of 60Hz is 395.5MB/s. 3 of those is about 1200MB a second, or over a GB of data. I'm not sure if you can send only the changed parts and have the monitor construct the proper image, but even if you can, one monitor with full screen video is still well above USB2's bandwidth. USB 3.0 is much higher, but still not 1GB/s. I'm not sure how this'll work out for you, but even in a best-case scenario where you're getting maximum throughput and you're only sending the diff, I can't see you getting anywhere near decent performance.

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Why would you need to work the three monitors with a laptop? Surely the monitors aren't easily portable. Is it just cost? If so, bite the bullet and buy a small tower and three video cards.

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Or use one video card that can support three monitors –  Xantec Nov 2 '10 at 13:37
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I'm old--when I was learning this stuff, supporting ONE monitor was hard. And we had to read our monochrome screens while computing uphill both ways. Good point. –  CarlF Nov 2 '10 at 14:56
    
-1...I have tons of people who want to use 3 at home and 3 at the office. –  Shinrai Nov 3 '10 at 14:29
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Wow, your company has too much money. –  CarlF Nov 3 '10 at 14:35
    
"while computing uphill both ways" lol. –  Trevor Boyd Smith Jun 6 '11 at 13:07
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I have used four of these on a single laptop and not had any performance issues. (This was a Thinkpad W510 with 16GB of RAM so your mileage may vary...I've done two and three on lesser machines and/or through docking stations though) The max throughput of the USB bus is indeed way less than these could theoretically push but they don't have any hardware acceleration anyway, so it's largely a moot point since DisplayLink has written their driver pretty well.

Also, USB 3.0 adapters will be coming out soon and they can push more bandwidth than you'll need over the bus anytime soon.

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