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There's no interop story between Thunderbolt and USB. Thunderbolt is packetized PCIe over USB-C connector in the alternate mode, that's all, similar to DisplayP

There's no interop story between Thunderbolt and USB. Thunderbolt is packetized PCIe over USB-C connector in the alternate mode, that's all, similar to DisplayPort over USB-C. Even the cable is different than USB. With TB, you know exactly what are you getting. On the connector, there's a flash icon (meaning: thunderbolt) and a number (if > 3). That number says, which TB version it is. Even with USB4, there's no convergence. USB4 made TB alternate mode optional. USB4 is no guarantee, that you can use TB.

ajross 3y ago
> With TB, you know exactly what are you getting. The article is literally detailing a Thunderbolt device that behaves differently when plugged into different macs, precisely because of the ambiguity introduced by the USB4 modes. "You know exactly what you are getting" is a story about a specification being unambiguously written. It doesn't say anything about what happens when you have dueling specs on the same port, which is the problem here.
- vetinari 3y ago
  The article is detailing a device that has dual protocol support: TB and USB. It prefers TB in one case and USB in another. I don't see any ambiguity here: it goes down the list: USB 4, TB, USB 3.1. The Intel macs are missing USB 4.
  - ajross 3y ago
    > [big list of specifics about what works where] So, you agree that the specification landscape is a soup of incompatible variants which make practical interoperability mostly a crap shoot for consumers. You just don't think that's a problem?
    - CharlesW 3y ago
      I believe he's responding to the characterization of the drive as a "Thunderbolt device". As the article and @vetinari note, the drive supports both Thunderbolt and USB. It's sort of a given that that performance would be different based on which "mode" it's in. One related complication of sharing a physical standard is that all Thunderbolt 4 cables work for USB 4, but the reverse isn't true. Ideally that would not be the case, but people want their cheap USB cables.
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- paulmd 3y ago
  > With TB, you know exactly what are you getting. On the connector, there's a flash icon (meaning: thunderbolt) and a number (if > 3). That number says, which TB version it is. that's absolutely not true at all - for example, cables can be either active or passive, which is not denoted on the cable. Many devices will not work over a passive cable, because it does not provide power.
jeffbee 3y ago
> Thunderbolt is packetized PCIe over USB-C It is not this. PCIe can be encapsulated over a Thunderbolt connection, but that is not what Thunderbolt is. Thunderbolt is Thunderbolt.
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ajross 3y ago

> With TB, you know exactly what are you getting. The article is literally detailing a Thunderbolt device that behaves differently when plugged into different macs, precisely because of the ambiguity introduced by the USB4 modes. "You know exactly what you are getting" is a story about a specification being unambiguously written. It doesn't say anything about what happens when you have dueling specs on the same port, which is the problem here.

vetinari 3y ago
The article is detailing a device that has dual protocol support: TB and USB. It prefers TB in one case and USB in another. I don't see any ambiguity here: it goes down the list: USB 4, TB, USB 3.1. The Intel macs are missing USB 4.
- ajross 3y ago
  > [big list of specifics about what works where] So, you agree that the specification landscape is a soup of incompatible variants which make practical interoperability mostly a crap shoot for consumers. You just don't think that's a problem?
  - CharlesW 3y ago
    I believe he's responding to the characterization of the drive as a "Thunderbolt device". As the article and @vetinari note, the drive supports both Thunderbolt and USB. It's sort of a given that that performance would be different based on which "mode" it's in. One related complication of sharing a physical standard is that all Thunderbolt 4 cables work for USB 4, but the reverse isn't true. Ideally that would not be the case, but people want their cheap USB cables.
- deleted 3y ago
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paulmd 3y ago
> With TB, you know exactly what are you getting. On the connector, there's a flash icon (meaning: thunderbolt) and a number (if > 3). That number says, which TB version it is. that's absolutely not true at all - for example, cables can be either active or passive, which is not denoted on the cable. Many devices will not work over a passive cable, because it does not provide power.

jeffbee 3y ago

> Thunderbolt is packetized PCIe over USB-C It is not this. PCIe can be encapsulated over a Thunderbolt connection, but that is not what Thunderbolt is. Thunderbolt is Thunderbolt.

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