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105 comments
da_667

@catsalad LISTEN. THE STANDARD SAYS 127 devices...

basisbit 🦈🇪🇺🇺🇦

@da_667 @catsalad
The standard also says a maximum depth of usb hubs of 3 afafik

Biggles

@basisbit @da_667 @catsalad even then it is unreliable e.g. laptops like to build hubs into themselves (we have this problem with the work setups)

basisbit 🦈🇪🇺🇺🇦

@Taco_lad @da_667 @catsalad
Usually I would not link to him, but.... LinusTechTips recently made a video explaining this a bit:
youtube.com/watch?v=hiwaxlttWo #usb

Agnieszka R. Turczyńska

@Taco_lad @basisbit @da_667 @catsalad I have shared the picture with a friend, and he answered: "You want to kill me". Then he shared the picture with his friends and get back to me with some informations. I will use that as an excuse to enlighten you. However, if you are already USB expert, you may safely skip to the end of this toot.

So, this is how it goes.
This is maximum you can achieve using those hubs. You can have 7 layers of devices in USB, however host and root count as a layer themselves. That lefts us 5 layers to use. Sometimes the device has a hub build inside, which takes another layer.

Each hub can have 7 ports at most, but because of reasons (unknown to me) hubs with more than 4 ports have two 4-ports chained together.

In theory, using the device tree as effectively as possible, one can connect 117,649 devices to the single controller, however there is a limit implemented in many of the controllers, as they can handle up to 128 devices.

Allegedly, the newest AMD chipsets can handle 512 devices.

So, this is what I've learned today. And if I need this knowledge even after, that means something went really, really wrong.

Enjoy your day, fellow nerdy people.

PS. Does anyone know a technique to remember the number 117,649?

@Taco_lad @basisbit @da_667 @catsalad I have shared the picture with a friend, and he answered: "You want to kill me". Then he shared the picture with his friends and get back to me with some informations. I will use that as an excuse to enlighten you. However, if you are already USB expert, you may safely skip to the end of this toot.

HansvR

@agturcz I would just remember it, but tomorrow I've forgotten your name.

David JONES

@basisbit @da_667 @catsalad I think you could achieve that with an even more cursed arrangement.

artemist

@basisbit @da_667 @catsalad The max depth is 7 and it's somewhat artificial, if you patch the kernel you can get around it.

✧✦✶✷Catherine✷✶✦✧

@artemist @basisbit @da_667 @catsalad for USB2 it's based on turnaround time and cable length; it's not really artificial so much as there's margin available (which you can hack away)

[SUYA] ひみつ :blabcatverified:
@da_667 @catsalad the standard also says max 7 devices in a chain (pc + 5 hubs + 1 end device in this case)

although I think they're called classes or something in the spec, I don't really remember
Noodles

@da_667 @catsalad For some reason, I have a very distinct memory of @leo talking about this on the Screen Savers in like, the 90s, and I am still, to this day, disappointed that every USB device does not include a port allowing you to just, continuously daisy chain Mice and Keyboards.

Instead, modern computers can barely be assed to give us one port on the machine itself.

ballpointcarrot

@catsalad
Why do I hear Ozzy Osbourne quietly playing somewhere?

DELETED

@catsalad Since it always takes three attempts to plug in a USB-A connector, someone have been busy 😅

Dr. Mastodonocologist

@catsalad
Aaaaaahhhhhhhhhhhhhhhhhhh!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ebeeto

@fcktheworld587 I hate how this was the first thing I thought of too. I need less Internet in my diet.

bytebro

@catsalad Good grief. "There's a cleaner way to do that!"

A.Krontab

@catsalad I reflexively blurted out "Oh Fuck You!" The second I saw that.

Well played.

Willi

@fbarton @catsalad just checked if anybody made this comment.

Scott :clippy:

@catsalad pretty sure i saw this exact setup as a diagram in the usb 1 spec back when

Alex Savage

@catsalad I see you've discovered my production file server with RAID 5+0

Alex Savage

@catsalad ahh, that's a good TEMPDB right there. you just replace the individual microSDs when they start smoking

DELETED

@optimant @catsalad I shit you not, a coworker who worked in the IT department found a stash of IOMega zip drives that he chained into a mac made a raid 5 out of.

Writing a single logical block was the sound of Armageddon, and it took twice as long.

Rui Malheiro

@catsalad it's not a train. It's a bus. A five decker bus.

xek

@catsalad I want to say "lsusb or it didn't happen" not because I disbelieve you, but because I Don't Want To Believe.

Billy O'Neal

@catsalad How cursed does something have to be to open a portal to the dark dimension?

Billy O'Neal

@catsalad I don't know what I'm looking at on this one. Can it truly compete with a 5x USB multiplier?

Jessie Nabein

@catsalad @malwareminigun yum, security juice! :blobfoxterrified: :blobfoxscared: :OhNoBubble:

Billy O'Neal

@jasonnab @catsalad I have a suspicion I would find this a lot more cursed if I had any idea what the black thing was

Jessie Nabein

@malwareminigun @catsalad i believe that is a security camera :blobfoxlaughsweat:

remote procedure chris

@catsalad easy & cheap way to get 6x the power out of one usb port but the fossil fuel lobby doesn't want us doing that

gobborg

@catsalad when the universal serial bus becomes a universal serial train

terra tauri (she/her)

@catsalad helm charts that have a value that takes YAML

rancher using docker to run docker to run kubernetes so you can run docker

using rust to output WASM and then running it in firefox

DELETED

@catsalad I’m so confused 🤣 am I seeing a good & upright thing here, or is this darkest evil? Was a kettle offscreen right being boiled?

Mary DeVries

@catsalad what this really needs is a Lego mini figure climbing the stairs.

DELETED

@catsalad ❌ Universal Serial Bus
✅ Universal Serial Train

Raymond Russell

@catsalad
Looks dodgy.....hope you understand the gravity of the situation😃

mirabilos

@catsalad did I mention just how much I dislike USB?

John Helt

@catsalad "Hello, Tech Support? I need a new laptop. The USB port is intermittent and only works if I jiggle it "

screw_dog

@catsalad "is this the bus parking?" - my child

Patrick Chizeck

@catsalad

Curious what would happen if I tried this.

eyrea

@catsalad The initial connection at the very least had to be sealed with super glue for the weight not to tilt the stack out of the socket

Aviva Gary

@catsalad Did a blackhole open somewhere or is it just me... 👀

CDCastillo

@catsalad it made me think of a terror movie 🍿 🎥

Kai Mast

@catsalad Whats the bandwidth on the last cable?

Rachel Greenham

@catsalad @mcc for the love of god, just give up and get a hub! 😅

Panama Red

@catsalad Can the bus even hold all those passengers? 😉

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