Thunderbolt speed

[Deleted member 4644]

http://developer.apple.com/library/...s.html#//apple_ref/doc/uid/TP40011138-CH2-SW5

can someone confirm the speed of a current Thunderbolt cable (single direction). I think it is 10 Gb/sec or roughly 2.56 lanes of PCIE 2.0.

Is that right?

10 gigabit = 1280 megabytes.

Pcie 2.0 lane is 500 MB/sec ( http://en.wikipedia.org/wiki/PCIE )

So 1280/500= 2.56.

Does that sound right?

So the next gen Thunderbolt (20gbs) should be around 5.12 lanes of PCIE 2.0?




Question 2:

Would 5.12 lanes of PCIE 2.0 be enough for a modern mid-high gaming card?

 

[TheReaWarmonger]

1 Gbit = 125 MB
10 Gbit/s = 1250 MB/s
1 Channel = 1250 MB/s
20 Channels = 25,000 MB/s
PCIe 2.0 x1 = 500 MB/s
PCIe 2.0 x16 = 8000 MB/s

So Thunderbolt is roughly equal to 50 lanes of PCIe 2.0 at full capacity. Explains why the Thunderbolt wiki states it uses 4x PCIe 2.0 since 3 would fall short (48 lanes). Or exactly 2.5 lanes of PCIe 2.0 running under 1 channel. Your math is right, just understanding of a gbit is a bit off.

 

[TheStu]

http://developer.apple.com/library/...s.html#//apple_ref/doc/uid/TP40011138-CH2-SW5

can someone confirm the speed of a current Thunderbolt cable (single direction). I think it is 10 Gb/sec or roughly 2.56 lanes of PCIE 2.0.

Is that right?

10 gigabit = 1280 megabit.

Pcie 2.0 lane is 500 MB/sec ( http://en.wikipedia.org/wiki/PCIE )

So 1280/500= 2.56.

Does that sound right?

So the next gen Thunderbolt (20gbs) should be around 5.12 lanes of PCIE 2.0?




Question 2:

Would 5.12 lanes of PCIE 2.0 be enough for a modern mid-high gaming card?

To answer question 2: http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/23.html

TL;DR, at PCIe 2.0 x4, you are looking at about 5-15% loss compared to x16

The issue right now with Thunderbolt externals is that only so many systems even have Thunderbolt, and the existing enclosures are expensive. Then there is the power consideration.

 

[Deleted member 4644]

1 Gbit = 125 MB
10 Gbit/s = 1250 MB/s
1 Channel = 1250 MB/s
20 Channels = 25,000 MB/s
PCIe 2.0 x1 = 500 MB/s
PCIe 2.0 x16 = 8000 MB/s

So Thunderbolt is roughly equal to 50 lanes of PCIe 2.0 at full capacity. Explains why the Thunderbolt wiki states it uses 4x PCIe 2.0 since 3 would fall short (48 lanes). Or exactly 2.5 lanes of PCIe 2.0 running under 1 channel. Your math is right, just understanding of a gbit is a bit off.

The current implementation can only address 1 channel per divice. The upcoming revision will double the speed however to 2500MB sec or 5x PCIE 2.0.

 

[pandemonium]

Question 2:

Would 5.12 lanes of PCIE 2.0 be enough for a modern mid-high gaming card?

Here's your answer.

Moving from PCIe 2 x16 (8GB/sec) to PCIe 2 x8 (4GB/sec) does incur a generally small penalty on the 7970. However like most tests this is entirely dependent on the game itself. With games like Metro 2033 the difference is non-existent, while Battlefield 3 and Crysis only lose 2-3%, and DiRT3 suffers the most, losing 14% of its performance. DiRT3’s minimum framerates look even worse, dropping by 19%. As DiRT3 is one of our higher performing games in the first place the real world difference is not going to be that great – it’s still well above 60fps at all times – but it’s clear that in the wrong situation only having 4GB/sec of PCIe bandwidth can bottleneck a 7970.

Finally if we take one further step to PCIe 3 x2 (2GB/sec), we see performance continue to drop on a game-by-game basis. Crysis, Metro, Civilization V, and Battlefield 3 still hold rather steady, having lost less than 5% of their performance versus PCIe 3 x16, but DiRT 3 continues to fall, while Total War: Shogun and Portal 2 begin to buckle. At these speeds DiRT3 is only 72% of its original performance, while Shogun and Portal 2 are at 81% and 92% respectively.

Ultimately what is clear is that 8GB/sec of bandwidth, either in the form of PCIe 2 x16 or PCIe 3 x8, will be necessary to completely feed the 7970. 16GB/sec (PCIe 3 x16) appears to be overkill for a single card at this time, and 4GB/sec or 2GB/sec will bottleneck the 7970 depending on the game. The good news is that even at 2GB/sec the bottlenecking is rather limited, and based on our selection of benchmarks it looks like a handful of games will be bottlenecked. Still, there’s a good argument here that 7970CF owners are going to want a PCIe 3 system to avoid bottlenecking their cards – in fact this may be the greatest benefit of PCIe 3 right now, as it should provide enough bandwidth to make an x8/x8 configuration every bit as fast as an x16/x16 configuration, allowing for maximum GPU performance with Intel’s mainstream CPUs.

 

[Montosaurous]

I think thunderbolt is 10 GB/s, faster than USB 3.0

 

[Cerb]

http://developer.apple.com/library/...s.html#//apple_ref/doc/uid/TP40011138-CH2-SW5

can someone confirm the speed of a current Thunderbolt cable (single direction). I think it is 10 Gb/sec or roughly 2.56 lanes of PCIE 2.0.

Is that right?

10 gigabit = 1280 megabit.

Pcie 2.0 lane is 500 MB/sec ( http://en.wikipedia.org/wiki/PCIE )

So 1280/500= 2.56.

Does that sound right?

10Gbps = 1GBps. You divide by 10.
http://www.google.com/patents/US4486739
^ That's why PCIe, USB 3, DVI, DP, and so on, have nice even ending digits for their bandwidth.

1 TB channel = 10Gbps = 1250 Mbps
1x PCIe 2 lane = 500MBps = 625Mbps
1250/625 = 2

 

[piasabird]

Intel had a prototype at computex of a 20Gbs flash drive based on thunderbolt 2 interface.

http://www.tomshardware.com/news/Thunderbolt-USB-Thumbdrive-Computex-Prototype,23001.html

Its on the Internet so it must be true . . . .
2 lanes of traffic.

 

[piasabird]

Can a drive actually run at the speed of the interface is another question.