Please clarify how Multi-seat works...??? [LWN.net]

Please clarify how Multi-seat works...???

Posted May 2, 2012 18:30 UTC (Wed) by pr1268 (subscriber, #24648)
Parent article: Poettering: The Most Awesome, Least-Advertised Fedora 17 Feature

Allow me to understand correctly: Is that multi-seat "Pluggable Universal Laptop Docking Station" (on the Amazon.com link above) just like a KVM switch with network (RJ-45 jack, I presume), and sound (3.5mm stereo mini-plugs for both output sound and input/microphone)? And it all works via USB 2.0?

If so, then fascinating! (I should crawl out from under the rock I'm living every so often. ;-) )

P.S. I'm assuming it's not limited to just a laptop; i.e. desktop workstations could also make use of this, as Lennart's article suggests.

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Please clarify how Multi-seat works...???

Posted May 2, 2012 19:19 UTC (Wed) by drag (subscriber, #31333) [Link]

Internally it will be basically two hubs

USB 2.0 port from PC ---> HUB1 --> Displaylink USB + USB Ethernet + USB Audio + USB HUB2 ---> 4 USB ports.

Yeah it's pretty awesome considering how little bandwidth you have to work with. USB 2.0 is about 60MB/s rate with the ability to push about 30-40MB/s if your lucky. Seems like USB harddrives stick around 20-25MB/s

When USB 3.0 and/or thunderbolt devices start coming out it's going to be even cooler. :) USB 3.0 should get you around 300-450MB/s of real-world bandwidth.

Thunderbolt seems like it has the potential to be a universal interface. So you would end up with a single chip on your computer that would provide all your basic I/O functions of network/SATA/digital display/USB 3.0/PCI-E all multiplexed over one type of external port and one type of cable. (thunderbolt devices demultiplex internally)

Please clarify how Multi-seat works...???

Posted May 2, 2012 21:25 UTC (Wed) by raven667 (subscriber, #5198) [Link]

> Thunderbolt seems like it has the potential to be a universal interface.

For some reason probably related to network effects of existing deployed systems this never seems to work out in practice. Before Thunderbolt there was Firewire and before that SCSI and the granddaddy of them all Ethernet but none became a universal connector standard. The most successful has been USB, which was only built as a reaction to non-technical issues with Firewire.

USB has very successfully targeted low bandwidth devices. even USB2 isn't even as fast as the original Firewire 400 from the 1990s . I don't see Thunderbolt or another connector replacing it anytime soon, there are still going to be a smattering of different connectors such as Thunderbolt, eSATA, USB and Ethernet for the foreseeable future.

Please clarify how Multi-seat works...???

Posted May 2, 2012 21:43 UTC (Wed) by engla (guest, #47454) [Link]

Thunderbolt is both a display cable and a data cable, which is more than USB or Ethernet.

Please clarify how Multi-seat works...???

Posted May 2, 2012 23:25 UTC (Wed) by drag (subscriber, #31333) [Link]

[quote]
USB has very successfully targeted low bandwidth devices. even USB2 isn't even as fast as the original Firewire 400 from the 1990s . I don't see Thunderbolt or another connector replacing it anytime soon, there are still going to be a smattering of different connectors such as Thunderbolt, eSATA, USB and Ethernet for the foreseeable future.[/quote]

That is why you'd do things like have a USB 3.0 controller or eSATA controllers that plug into your thunderbolt port. :) It's not going to replace any of that. It's just going to allow you to plug in fiendishly large amounts of devices into you computer.

With 2 thunderbolt ports you could do things like connect up to 12 ethernet cards. If you have ones that have two ethernet ports then that is 24 ports, which would make for a cheap 24 port Linux router for a 1Gp/s network.

Also you can use it in conjunction with IOMMU and hand over PCIe devices you plug into the thunderbolt port to your KVM virtual machines.

What it really boils down to is cost. If the demodulate chip for thunderbolt and wiring costs too much then nobody will use it.

Thunderbolt

Posted May 8, 2012 8:36 UTC (Tue) by job (guest, #670) [Link]

You can already see this with Apple computers. They didn't offer docking stations for their laptops, which I thought was a shame, but now they do offer Thunderbolt connectors instead. The monitor becomes the docking station where keyboard and ethernet is constantly connected. You can even keep it when you change laptop models! Connecting more than one head per computer could hopefully be a natural extension of this.