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Mac Pro – arstechnica Review
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I think Thunderbolt is bi-directional so a total of 40 gbit/s. In reality with overhead taken into account I think this translates to a peak of about 1.5GB/s (1500 MB/s). So, uncompressed 6K would handle roughly 13 fps fully uncompressed, 4:4:4 16bpps if the previous figures are correct.
Not sure that’s the case with RED RAW. Downstream is much lower as I presume the RAW-file is sent at its 1/5 the size or similar (i.e up to 60 fps). Back to local storage, if they actually do send it 100% uncompressed you’d be stuck at about 50% of real time. I’d image even lossless compression could bring the file size down by 50% almost giving realtime.
All in theory of course.
If compression and scaling is handled by the card, going to anything below uncompressed 4:4:4 16bpp RGB 6K (which to be fair is what most people do) should give realtime performance. At sort of depends where things happen in the pipeline. Most people would probably go from 6K to 1080p where I’d imagine scaling is done on the card hence only a 1080p uncompressed stream comes back over TB.
Playback of R3D media even at 6K should be realtime as downstream we’re talking 1/5 of the bandwidth.
I also think Thunderbolt 2 supports port aggregation. Linking two ports could potentially handle 6K uncompressed, in theory.
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[Erik Lindahl] “I think Thunderbolt is bi-directional so a total of 40 gbit/s.”
For what I understand TB2 is the same as TB1, with the only difference that TB1 has two 10 gig channels, one for each direction, and TB2 combines those 2 channels into one stream if it’s unidirectional.
This is from wikipedia:
At the physical level, the bandwidth of Thunderbolt 1 and Thunderbolt 2 are identical, and Thunderbolt 1 cabling is thus compatible with Thunderbolt 2 interfaces. At the logical level, Thunderbolt 2 enables channel aggregation, whereby the two previously separate 10 Gbit/s channels can be combined into a single logical 20 Gbit/s channel.
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[Gustavo Bermudas] “For what I understand TB2 is the same as TB1, with the only difference that TB1 has two 10 gig channels, one for each direction, and TB2 combines those 2 channels into one stream if it’s unidirectional.”
That’s incorrect I think.
[Anandtech] “Thunderbolt 2 provides that solution. By combining the channels together, Thunderbolt 2 enables two 20Gbps bi-direction channels instead of two sets of 10Gbps channels. There’s no overall increase in bandwidth, but the solution is now more capable.”
Aanandtech.com: Thunderbolt 2 Everything you need to know
Even looking at Intels info we get the same data.
Thunderbolt 1 has 4×10 Gbps – two upstream, two downstream
Thunderbolt 2 has 2×20 Gbps – one upstream, one downstream -
No, it’s the same aggregate as TB1, that graph can be misleading.
ATTO released a document detailing the differences
https://www.jigsaw24.com/news/wp-content/uploads/2013/12/TechBriefThunderboltComparison1.pdf
Also another view on the topic:
It seems that TB2 is designed with the only purpose of supporting 4K Displays
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[Gustavo Bermudas] “No, it’s the same aggregate as TB1, that graph can be misleading.
ATTO released an extensive document detailing the differences”
Yes, TB1 and 2 have the same total bandwidth. Even the ATTO document states this.
“Thunderbolt exists as (4) fully independent 10Gbps channels ‐ two upstream and two downstream (see left side of diagram below).”
“Thunderbolt 2 enables (2) 20Gbps bi‐direction channels (see right side of above diagram) instead of (4) of 10Gbps channels.”
Intels diagram and what ATTO writes sounds quite crystal clear to me. Even the second link states exactly the same thing.
“Thunderbolt 1 has 4 independent 10 Gb/s channels, Thunderbolt 2 combines these to give 2 20 Gb/s bidirectional channels“
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[Gustavo Bermudas] “Of course they’re going to say that, they’re not going to discard the whole Mac user base, and while you can run that card in TB, you’re never going to get the same performance you can get running on a fast PCI bus.”
Of course TBolt has limits, but look at the form factor. And real time is real time. You mentioned real time, so I am using that as the bench mark.
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Hey Erik,
I just saw this video and remembered our little “discussion”, 7 minutes into the video he mentions mac pro’s are able to use as renderfarms by linking them over thunderbolt and according to this man it works very well.
It also puts things in a different perspective as you can now suddenly have a 24 core machine for $13000, and go up to… I guess 6×12=72 cores for $39.000? But in any case, 24 cores for 13000 doesn’t sound like a bad deal
here’s the link to the video (at 7mins):
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Yeah I saw that clip the other day. I have however read numerous reports of very poor speeds, or rather unreliable speeds over TB networking.
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In that case I hope over time they can make it work properly.
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