How many logical hubs is it?
(For example, a typical 7-port hub is two logical four-port hubs, with hub #2 "plugged" into a port of hub #1, leaving seven open ports for the user.)
Reason I'm asking is, the Raspberry Pi can have issues with this hub if there are too many logical hubs inside it.
I think they are three logical seven-port hubs. So each hub used counts as 21 usb ports with 19 usuable. Razorfish correct me if i am wrong here!
The hub is 19 external USB ports , 3 are level 1, 16 are level 2… that is all we need to care about… for expansion hubs plug the shit into the side.
This is something I have been HARPING on for over a YEAR on the forums and WHY the Pi is NFG for large installations.
Most of these shitty little 'cutter' SBC's have major problems with the USB… then add into this equation SHITTY hubs.
Nearly everyone knows about the 126 USB device limit per Physical controller, but what is not often discussed it the level limitation.
'Theoretically' a usb chain can be nested to upto 5 levels.
I.E
Controller+Hub+hub+hub+hub.
Now here is the rub… inside the silicon of the SBC or sometimes on the PCB is a hub chip (NOT for users)…, because these SBC devices CHAIN the ethernet/bluetooth or other I/O internally off the USB protocol, just the manufacturers don't tell you directly….
So what they do is 'hide' as many as TWO logical USB hubs INSIDE the SBC (Huba Huba), BUT then Chain them off each other and into a SINGLE silicon port……,
The reason why they hide two, is because as soon a you plug a slow device into a chain then the WHOLE chain is that speed(new smarter hub chips can act as translators without destroying the speed of the whole chain as long as there is a clear path at 480Mb/s).
The net effect of this SBC hand job is that straightway the 5 levels become 3 or less!!!, which is basically enough for 1 extra 10 port hub (because 1 chip HAS to be chained off another one and hence the problems with the PI, if you are lucky you plug the other hubs into the FIRST chip in the chain then you get a second level, if not they get plugged into the second chip and go out of range)
Coming back to the metal hub:
if you use the 3 side connectors, then it is one level ,
if you use the top, then it is basically 2 levels apart from 2 top ports where it is 1.(work it out!! )
So… if you buy 4 metal hubs
you plug your computer into one of the hubs via the 'B' type connector and then you plug the other THREE hubs into the side connectors of that ONE hub, UNLESS your computer has more than 1 port, in which case you use ALL the connectors on the computer first.
DO NOT build up a single chain of 1:1:1:1 and think it is cooler and faster, because it is not.
USB is a TREE structure and no tree has all the branches on a single limb (consider the controller as the TRUNK, notice how mother nature has ALL this 'effective distribution' shit already worked out!!!).
These metal hubs I PERSONALLY have had a full device chain of nearly 126 devices, the miner count reached ~104 devices, the rest was hub chips………
But NOTE, the miner performance is less with an SBC than a 'real computer', I suspect it is due to kernel task switching.
Next up……..
Realtek, yep you see they make all sorts of USB silicon…. In fact they developed a shit load of silicon when USB 1.0 came out, and since silicon development is expensive, when USB 2.0 came out they took a silicon 'wrapper' that runs USB2.0, but then the internal cores of their chips are USB 1.0…., their chips are mostly used in cheap crap hubs from China.
BUT they all advertise the products as USB 2.0 compatible with 1.0, because the silicon wrapper is good to USB2.0 standard (which Is compatible with 1.0) ,but the actual internal core silicon communicates at 12mb/s or SLOWER!!!.
Same with their Ethernet to USB chips, the whole core runs at USB1.0, which is ironic because the Ethernet is '100/10 compatible' but it is bottlenecked because it is running at USB1.0 speeds internally!!!!
(bit like some old lady driving her battery powered trike in a 45MPH zone, because it is 'road worthy' but holding up all the traffic behind her)
Needless to say Microsoft was involved in this…..