Thunderbolt is bi-directional so it can push 10Gbps in both directions at the same time.
I know that.
Keep in mind however, it can only run bi-directionally under certain conditions:
- Is the end-point technology it's connected to capable of bi-directional communication simultaneously?
- How many other devices are connected at the same time?
- How are they being accessed (% of read v. write)?
Let's take storage for example. Even though it's bi-directional, it can only read or write per operation, not both at the same time. And it's not alone.
Now if you've multiple storage devices (or other types of products attached to TB and being used simultaneously), there is the possibility that you'd be able to utilize TB's bi-directional capability simultaneously. But it will depend on the specifics every time a TB device or group of TB devices are being used.
But statistically speaking, most will likely only benefit from one direction at a time, which makes the 10Gb/s throughput limit of a single direction more important than it's combined throughput.
This is why I suspect Intel has published the 10Gb/s figure rather than advertising 20Gb/s (rather surprised at this actually, as marketing depts. would usually latch onto the higher value). Which lends me to think that someone in management was paying attention, and didn't want such a "stretching of the truth" to cost them in the long run.
You're forgetting the effect of cache.
The testing I saw was based on the drives they shipped in the unit, which were Hitachi
Deathstars Deskstars at that time.
They're certainly not shoving SSD's into it for the base MSRP.
As per the details of the Anandtech article, we can go into that if you want, but here's a hint:
Each 10GB/s lane, even though is listed as bi-directional, can only run in a single direction at once, just as is the case with many other bi-directional technologies. Strapping dedicated lanes is required, and is also the case with TB.
For example, if you're running a single TB port bi-directionally, one of the 10Gb/s lanes will be used for up traffic, and the other for the down traffic. They could have made it more robust in regard to how it handles traffic, but that would have added complexity, and therefore cost to a product that was already over budget, and cut the optical portion of the spec, primarily to keep component costs within a range that vendors/board makers will bite.