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Frank Gothmann
Daisy chaining TB devices
on Jan 30, 2012 at 8:02:54 pm

Preliminary answer to my question how several TB devices chained together affect performance.
Apparently, dual monitor setup, video io and Raid isn't going to fly via one controller.

http://fcp.co/hardware-and-software/pro/715-does-thunderbolt-slow-down-when...


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Lance Bachelder
Re: Daisy chaining TB devices
on Jan 30, 2012 at 9:58:27 pm

I just read the article. Makes sense - although it's a big pipe it's still only one pipe. We wouldn't stack our graphics card, Kona 3 and fibre channel card into a single pci-e slot and expect everything to run at full speed?

An iMac has 2 Thunderbolt ports - are those separate channels?

Lance Bachelder
Writer, Editor, Director
Irvine, California



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Walter Soyka
Re: Daisy chaining TB devices
on Jan 30, 2012 at 11:23:58 pm

[Lance Bachelder] "An iMac has 2 Thunderbolt ports - are those separate channels?"

Yes [link] -- though I'm not sure if the bottleneck in the other article was the the number of channels, the Thunderbolt controller itself, or the the TB controller's connection to the mainboard. Hopefully the iMac's additional two lanes will provide the needed bandwidth.

Regardless, the order in which devices are chained seems to matter quite a bit. Troubleshooting this is going to be like SCSI all over again. The more things change, the more they stay the same.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Jeremy Garchow
Re: Daisy chaining TB devices
on Jan 30, 2012 at 11:28:15 pm

It's not too shocking actually, that means three monitors are running, the two TB monitors and the laptop.

That's a lot to ask of a laptop if you ask me.


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Lance Bachelder
Re: Daisy chaining TB devices
on Jan 30, 2012 at 11:44:39 pm

Yes it seemed to work well with 1 extra monitor and 1 RAID which seems like a real world set-up for portable editing?

Lance Bachelder
Writer, Editor, Director
Irvine, California



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Jeremy Garchow
Re: Daisy chaining TB devices
on Jan 30, 2012 at 11:47:16 pm

A monitor, a raid and a io device still clocks over 400 MB/sec.

Jeremy


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Walter Soyka
Re: Daisy chaining TB devices
on Jan 31, 2012 at 12:20:15 am

Absolutely. Two displays plus peripherals is asking for a lot of bandwidth. It's a torture test -- probably the worst possible case for this TB controller, and not what I'd consider a real-world scenario. It's good to know what the limits are, but I don't think they're troubling at all.

I think the issues of what devices can be chained together and what order they must be chained in will be more troublesome for most users than running out of bandwidth.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Rick Lang
Re: Daisy chaining TB devices
on Jan 31, 2012 at 3:00:06 pm

Here is the carefully worded performance claim on the iMac which has two Thunderbolt ports:
"You can daisy-chain as many as six devices plus a display. The 27-inch iMac includes a second Thunderbolt port for even more expansion possibilities. Connect up to six more devices or a display or two."
Notice the last sentence which now says OR a display or two. Confusing since we know it could have said AND a display. It appears to me Apple is not claiming six devices and two displays on one port. On the iMac at least two displays should go on separate ports when there are several other devices on the chain for the port. Still I agree with the OP that Apple is claiming he should not have a problem but it may be that the particular devices are too demanding on the single port whereas some other devices may work such as the Matrox card and a Lacie drive. Apple is careful not to specify which combinations of actual cards work which would be feasible at the time they wrote the copy since there were only a few TB ready cards available.

Rick Lang

iMac 27” 2.8GHz i7 16GB


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