|Simply put, USB hubs DO NOT work with all USB devices - they never did, and they never will !|
By hub I mean the kind that has multiple ports that plugs into only one USB port, or that is wired up to only the pins for one USB port on a mboard header. External hubs you plug into only one port ARE that type of hub. Ports built into the front of a desktop tower case higher up MAY be that kind of hub. Additional USB ports in a printer or a keyboard or a scanner, etc., ARE that type of hub.
More things work with "powered" hubs that have an external power adapter connected to them so all ports can have up to 500ma each (usually they can't actually do that), but still, those do not work with everything.
Front USB ports on a desktop case, the ones that are lower down on a tower, are almost always individually wired to the pins for a port on the mboard - they are not in a hub of that type in that case. A port physically built into the mboard or a PCI controller card that is one of a pair that connects directly to a USB controller is not in that type of hub.
They stopped making PCI USB hub cards a long time ago, probably for that very reason!
All the ones you can get now are USB 2.0 Controller cards.
USB devices may not work correctly when they're connected to certain USB ports e.g. ports in a hub or on the front of a desktop case. If you have a desktop computer, you may have an IRQ sharing problem you need to fix, or your power supply may be starting to fail.
See response 3 in this:
Also - if you are using a USB extension cable, some of them have inadequate wiring and will not work properly with some USB devices.
The maximum amount of USB devices will work in ports that are built into the mboard, or in the ports built into the USB ports on a PCI USB 2.0 controller card.
For a desktop computer, USB ports that are connected to USB headers work fine with nearly everything too, IF the wiring between the header and the port is adequate - sometimes it is NOT.
If something won't work despite that, if you have a desktop computer, you may have an IRQ sharing problem you need to fix (see above).
If you don't have enough ports directly connected to the mboard, if you want the maximum of the USB devices to work....
- for a desktop computer, if you still have USB headers on the mboard you aren't using, get a 2 or 4 ports in a plate USB wiring adapter you install in a spare card slot , but be aware that some have inadequate wiring! The cables should have obvious wire shielding. If it has a one piece (e.g. 9 pin holes in a two row 5 each side connector) or two piece female connectors (e.g. a 4 in a row and a 5 in a row connector, or two 4 in a row) on the wiring, make sure it will work with the USB header on the mboard -that was never standardized - see the mboard manual, and the description of how the female connectors are wired. (Asus mboard USB headers work with the most common wiring adapter connectors - some other brands do not).
NOTE - if your mboard, e.g. Asus, has a firewire header, it's pin arrangement may be identical to that for a pair of USB ports! (it is for Asus mboards). Connecting USB ports to a firewire header or visa versa will fry whatever you plug into the mis-wired ports and damage the firewire or USB circuits in a very short time!
- for a desktop computer, get a PCI USB 2.0 controller card - 2 to 6 ports, up to 4 external, 2 internal, per card - but don't plug it into the last PCI closest to the center of the mboard - that slot shares it's IRQ with the video, and only PCI video cards are likely to work properly in it
- for a laptop computer, get a PCMCIA (PC Card) USB 2.0 controller card, or an ExpressCard USB 2.0 controller card - 2 to 4 ports per card - however, according to info I found they may have only 500ma available in total for all the ports on them, unless they also have a jack you can connect an external power adapter to (they don't normally come with the adapter).
When someone is having a problem accessing the data on a flash drive, external drive, or memory card, either
- the drive does not show up in My Computer or Windows Explorer
- or - it does show up but you can't access it's data properly ....
The flash drive (or external drive, or memory card reader) must be plugged into a port it will actually work in.
How to tell if the flash drive (or external drive, or memory card reader) is properly recognized as a hardware device, even if you can't access it's data.
Programs you can try to recover your data, if that's okay.
The most frequent reason people can no longer access the data on a USB flash drive, USB External drive, or a memory card
See Response 2:
External USB drives are a special case.
They frequently will not work when plugged into a hub, even if they can get 500ma from the port.
If you have an external drive, they must be able to get 500ma from the USB port(s) they plug into.
For an external drive that has a 3.5" drive in it, it's larger, it always comes with a power adapter, and...
The external drive MUST have the power adapter plugged into it's case and the power adapter must be powered and be working properly (it's common for people to damage the cord to the case because they pulled on the cord rather than the plug while unplugging it), AND the USB port you have it plugged into MUST be able to supply the standard max USB spec 500ma.
For an external drive that has a 2.5" drive inside of it, e.g. a "portable" drive, it's smaller, it does not normally come with a power adapter, it normally gets all it's power from the USB connection, and...
Some such external drives must be connected to TWO USB ports on the computer end, one of which can supply 500ma, or the total current available from the two ports can supply must be at least 500ma, or to one USB port and also have an external power adapter connected to a optional jack that's on the external case, in order for the drive to be recognized properly.
Some such drives come with two cords, for connecting to up to 2 USB ports on the computer end, or a Y cord that has a small USB connector on the external case end, two normal sized USB connectors for connecting to up to 2 USB ports on the computer end.
For some external enclosures, e.g. Vantec , and pre packaged enternal drives - one of the 2 USB connectors on the computer end is pass-through - other USB devices can be connected to it.
"my USB floppy drive does not work when other USB's are connected"
- if you are connecting to a desktop computer, you may have an IRQ sharing problem you need to fix
- you may need to re-load the USB stack
For both, see my first link above.
- rarely, one USB device can conflict with another one, for reasons that are a mystery to me (they use some same I/O address??). Sometimes you can do something about that, sometimes there is no cure.
e.g. I have a Logitech "combo" mouse that does that, only when one other USB device is connected (a controller for a flight simulator program you connect a real RC model plane flight controller to). If the two devices are connected, either one works, or the other, not both. They don't conflict with anything else USB I have. E.g. the mouse blinks it's led repeatedly while booting, which it does not normally do, but it works, the other thing won't work - or the other thing works but not the mouse.
There is no problem when I connect the mouse via it's USB to PS/2 adapter too a PS/2 port.
A "combo" mouse or keyboard is designed and wired up to work with two types of connections - usually these days that's USB abd PS/2 connections - the adapter that comes with them, or a generic adapter, will not work with amouse or keyboard that is not a combo mouse. An adapter for a"combo" mouse, often green, will often not work with a "combo" keyboard, and an adapter for a "combo" keyboard, often purple, will often not work with a "combo" mouse, because the proper wiring is not there within the adapter.