Blackmagic Forum

The question is about BMCC interfacing. Was it a good idea for BM to go along with thnunderbolt interfacing as many video facilities (like in my place) are equiped with PCs coming with USB 3.0 only ?

I don't think so and I haven't seen the huge wave of Thunderbolt implementation on Windows that we were anticipating a year ago.

then what are the best solutions to get the files on a desktop or a laptop PC ?

A USB3.0 or ESATA dock is the best way to get files transferred from your SSD...that's really not a big deal. I was thinking about UltraScopes and the lack of any USB3.0 implementation (that works).

Intel Haswell chipsets (launching early June) are going to start supporting thunderbolt natively. So look for more support on the PC side soon.

As for data transfer, USB 3.0 is plenty fine, unless you somehow are literally crunched for time (in the minutes) which is highly unlikely. Thunderbolt is necessary for Ultrascopes because Thunderbolt sends information continuously via stream, USB 3.0 does so using data-packets. Different technology.

Actually USB3 and Thunderbolt are very similar... Thunderbolt is small-cable version of PCI-Express :

Thunderbolt controllers multiplex one or more individual data lanes from connected PCIe and DisplayPort devices for transmission via one duplex Thunderbolt lane

Wikipedia

and USB3 is also somewhat of a copy of PCI-Express :

5 Gbit/s (electrically it is more similar to PCIe Gen2 and SATA than USB 2.0

Wikipedia

It's not by chance that USB3 is 5GBit/sec, that's also the speed of a 1x PCI-E lane in Generation 2 mode (although that's actually GigaTransfers/sec). In addition USB3 supports multiple transfer modes, namely isochronous, interrupt, or bulk transfer. Both isochronous and interrupt modes can be used for streaming data (low latency).

And finally... no system actually streams data instantaneously... they all utilise buffers, interrupts, negotiation and timing synchronization, all of which impact the latency of data throughput. Processing of data, regardless of what bus/source it originates on entails an interrupt being called so that the CPU can start manipulating that data.

Thanks for that, but I didn't claim that Thunderbolt streams data instantaneous, I said data is delivered in a continuous manner, and that USB 3.0 (well all USB tech practically) uses data packeting and is a primary reason why it's not (rather cannot) be used in the same way Thunderbolt is.

Purely for data transfer, these differences don't matter, to the OP of course.

innerspark, my post was attempting to demonstrate that USB3 can and is probably just as good as Thunderbolt when it comes to data streaming... and by extension that BMD probably chose Thunderbolt for another reason.

I'm fairly sure that Thunderbolt has an up stream and downstream 10GBit/sec and USB 3.0 shares its one 5GBit/sec (about to be doubled i recall though so is thunderbolt) between upstream and downstream. Thunderbolt also allows for easier dasiychaining, and has Displayport built into the spec (and therfore by extension HDMI with sound).

RAW at 30fps on a BMCC is 142 MByte/sec* or 1.13 Gbit/sec, 23% of USB3's bandwidth**, so duplex or not sufficient bandwidth exists to satisfy the stream's requirements and USB3's transfer modes would allow that stream to be delivered with low latency (especially given that it would occupy less than 25% of the medium's bandwidth).

* based on the size 30 BMCC DNGs occupy
** based on 5Gbit/sec, theoretical maximum after protocol overhead is probably closer to 4Gbit/sec.

I'm just saying that USB3's ability to stream data is unlikely to be the reason BMD chose Thunderbolt.

As long as you don't have super fast RAIDs on BOTH sides, USB3 will not be a bottleneck.
Normally ether the SSD or the drive/RAID on the other side is.

I will at this point point out that I merely was pointing out a technical difference between the two.

Though depending on what you are doing it may not be as hard to get close to it as merely taking a single stream of read/write from a RAID would suggest.

I don't beleive its hugely unusualy especially on Laptops for seperate USB ports (at least in 2.0) to share a single bus, so thats split. And once you have a RAID array and an I/O box for something you are already a lot closer to that 5Gb/s.

TB was most likely a choice based on maximum throughput. Think of it like IEEE1394, featured on plenty of cameras but your average store-bought PC didn't feature the socket (until much later on). I can buy TB based motherboards now with no issue, however if I was purchasing a pre-built workstation I'd have little chance to see it because at this point TB is for Macs and enthusiasts unlike the universally adopted USB.

Basically it's a bit ---- for a person who doesn't build their own systems or want to upgrade but it's not a bad decision on BMD's behalf.