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Portable USB 3.2 gen 2 Type C extensions cable

Discussion in 'Hardware' started by wyx087, 29 Dec 2020.

  1. wyx087

    wyx087 Homeworld 3 is happening!!

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    Can anyone shine any light on these extension cables?

    I want to bring out the rear IO type C port to somewhere easily accessible. I'm getting some strange results with 2 extension cables I've bought.

    I've got a NVMe to USB 3.2 gen 2 10 Gbps caddy, with a short ~15cm cable.
    • Without extension: expected 1000 MB/s on both Ryzen 3600 CPU port and RTX 2080 Ti USB-C port.
    • With extension A (some cheap generic, 50cm): on CPU port, drive seems to have connectivity issue, goes offline when accessed. Didn't test GPU port.
    • With extension B (50cm silver 10Gbps UGreen): 250 MB/s on CPU, 450 MB/s on GPU.
    • Retest without extension: same 1000 MB/s on GPU.

    Top, GPU port. Bottom, retest on GPU port.
    upload_2020-12-29_16-34-54.png


    Are these extension cables doomed to failure?
    But what might be the reason for difference in speed on different ports?
     
  2. David

    David μoʍ ɼouმ qᴉq λon ƨbԍuq ϝʁλᴉuმ ϝo ʁԍɑq ϝμᴉƨ

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    Thunderbolt cable?

    It'll carry anything USB can throw at it.

    I have a type c nvme caddy and the supplied cable was sh1te, so I just use a spare TB3 cable
     
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  3. Xlog

    Xlog Minimodder

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    In short - if you need an extension, use either an active cable or a hub.

    Your caddy is USB3.2G2, so 2x 5GBPS lanes, your second extension cable is USB3.1G2 - 1x 10gbps lane (confused? there is a rant thread on here somewhere about USB3 specs). So the extension prob does not have enough conductors for USB3.2G2 and/or controllers dont support USB3.1G2 so they negotiate down to USB3 speeds - 5gbps. Now why CPU is half the speed of GPU is hard to say, controller might not be as robust, lower quality connectors, the signal path is longer/more complex on motherboard or combination of the 3, resulting in data losses/re-transmissions. In either case, if I remember correctly, USB3.x specs don't even allow for passive extension cables.


    edit. got confused myself between f****** standards.
     
    Last edited: 29 Dec 2020
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  4. wyx087

    wyx087 Homeworld 3 is happening!!

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    Ok, thanks for explanation guys. I didn't know USB 3.2 gen 2 is completely different to 3.1 gen 2!
    I know USB spec doesn't allow for passive extension cables, but I only need about 30cm to get it from rear IO to somewhere accessible.

    I see "thunderbolt 3 extension cables" are still saying USB 3.1 gen 2 10Gbps rather than 3.2 Gen 2: https://smile.amazon.co.uk/s?k=thunderbolt+3+extension+cable&crid=38GELUHJKYBT8&sprefix=thunderbolt+3+ext,aps,148&ref=nb_sb_ss_ts-do-p_1_17
    Does this mean this will end up with same 5Gbps result on 3.2 g2?

    Ultimately, what can I do to allow easy access to the removable drive at its full speed?
     
  5. wyx087

    wyx087 Homeworld 3 is happening!!

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    Isn't 3.2 gen 1 and gen 2 just rename of 3.1 gen 1 and 2?
    https://www.tomshardware.com/uk/news/usb-3.0-usb-3.1-becomes-usb-3.2,38699.html
    https://www.cnet.com/how-to/usb-3-2-explained-making-sense-of-current-and-confusing-usb-standard/
    https://www.onlogic.com/company/io-hub/usb-type-c-and-usb-3-1-explained/

    Although this article suggests there is a difference between 3.1 Gen 1x2 and 3.1 Gen 2x1:
    https://www.kingston.com/unitedkingdom/en/usb-flash-drives/usb-30

    I'm really confused, should 3.1 Gen 2 cable work at full 10 Gbps on 3.2 Gen 2 hardware or not? Considering Thunderbolt 3 cables are mostly marked as 3.1 Gen 2.
     
  6. David

    David μoʍ ɼouმ qᴉq λon ƨbԍuq ϝʁλᴉuმ ϝo ʁԍɑq ϝμᴉƨ

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    A full fat TB3 cable will carry 40Gbps, but you have to be extra vigilant when shopping for one because there's a lot of shoddy marketing around thunderbolt cables. You'll often find 20Gbps or even 10Gbps in the small print, especially over 1 metre in length where 40Gbps requires an active cable at around £50. You can get full fat half metre passive cables much cheaper though.
     
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  7. Xlog

    Xlog Minimodder

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    It should, in theory. I'm guessing the confusion about the cables is the reason why most SS+ peripherals come with non removable cable
     
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  8. wyx087

    wyx087 Homeworld 3 is happening!!

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  9. David

    David μoʍ ɼouმ qᴉq λon ƨbԍuq ϝʁλᴉuმ ϝo ʁԍɑq ϝμᴉƨ

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    Do you want to borrow a 20Gbps cable to test speeds?
     
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  10. wyx087

    wyx087 Homeworld 3 is happening!!

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    Thanks. But I hope I can trust Amazon customer service. The cost of posting back and forth will be close to cost of a new cable.


    I did some more retest. Inconsistent is going to be the keyword here. I retested the cables again. Extension A still doesn't work, must be dud. The UGreen Extension cable now works at full speed........ occasionally, depending on whether I plugged it in on an odd or even in the last digit of nanosecond. Strangely, the CPU socket gives better write speed than read speed.

    Interestingly, using GPU-z (of all software), I was seeing graphics card USB-C powerdraw never go above 2.5w when bad speed happens. When I got lucky and it ran at full speed, power draw goes up to 4.6w maximum. Could it be a dodgy caddy?

    It's also not a bad connection. Because I tried unplug and replug at different connection points, I can't seem to find a pattern. I also can't get the same 500MB/s result on GPU today.

    Screenshot of some of the tests:
    Top row: CPU socket tests. Bottom row: graphics card socket test.
    Column 1 is baseline using provided 15cm cable. Column 2 and 3 are with the UGreen extension cable. Bottom right is where power draw did not exceed 2.5w, seen multiple times.
    upload_2020-12-30_13-46-38.png

    Conclusion: extension cable is no-go.
     

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