USB 1 & USB 2 compatibility.

  wint 07:28 13 Jan 2003
  wint 07:28 13 Jan 2003

Hi, I know that USB 2 is backwards compatible with USB 1.

What about running a 4 port USB hub plugged into a USB 2 socket on the PC.

If I plug 3 USB 1 devices and one USB 2 device, will they run at their own respective speeds or will there be a conflict?

I am thinking of a USB 1 modem, USB 1 WiFi device and a USB 2 scanner.


  €dstow 08:08 13 Jan 2003

A circuitous answer but USB hubs have always caused me problems.

Modems and scanners function much better being connected direct rather than through a hub (don't know about WiFi but that may be the same).

Why use a hub? You can get a 5 port USB2 PCI card from Scan click here for £16-45 inc. Item no. LN3683.


  Simon_P 08:13 13 Jan 2003

I dont think that you will have a problem, at worst, your scanner may defult to usb1.
Have you considered having a PCI USB2 card fitted instead, these can be 2 or 4 port many USB2 scanners come with one.

  wint 08:22 13 Jan 2003

I am awaiting delivery of a 4 port USB 2 card.

My scanner has - so far - been fine running from the powered hub.

I don't want to run too much from the PC because of the power considerations - also the layout of the study means if I go through a hub I have less trailing wires which keeps my wife happy :-)

I wonder if the hub may be affecting my WiFi setup?? Hmmm, see click here


  €dstow 08:35 13 Jan 2003

"if I go through a hub I have less trailing wires"


If you avoid the hub you have one less device which surely must mean less wires.


  MalcSP 09:05 13 Jan 2003

I note Edstow's response on installing a PCI card but is it not so that such cards cannot power the devices attached to them such as webcams, modems etc?
Also I sympathise with wint and trailing wires. A hub does allow you to conceal wires more effectively.

Please, Edstow, don't take this as a criticism in any way. I find your input to this forum invaluable, and the question is a genuine one.

  wint 09:14 13 Jan 2003

My PC is one side of the desk and the scanner, webcam and, because I currently only have 2 USB outs on the PC, WiFi device on the other side. Considering the mess of cables already loomed together, the extras may break the camels doo dah.

I think that a PCI USB out will derive power from the PC but I don't want to overload the power supply. I have read (on these pages) about the problems this can cause.

  siarad 09:48 13 Jan 2003

I did a topic on this. Why has Universal Serial Bus become hub centric with wires starring all over?. The whole idea was to cut down on wires by looping from one device to another, thus one wire. A very few manufacturers abided by this with monitors & keyboards but the rest refused giving us the worst of it, lots of wires & very restricted distance. I was chided for thinking it was a conspiracy, so it's just a coincidence we have this nasty situation. The standard laid down 127 devices connected to a bus which seemed plenty for most peeps. Further it laid down 500mA current supply, reducing power connections but that isn't much shared between all those, however intermediate devices could be bus powered or mains powered as necessary. The whole idea was simplicity in both connection & usage, a dream gone sour. For some reason there are two versions of USB 1, not entirely compatible too.

  €dstow 10:05 13 Jan 2003

Scanners, and quite possibly WiFi devices, can have a large power requirement such that they are powered from independent power supplies either as a transformer/rectifier plug top or intrinsic mains units (as common in scanners). It is entirely unsuitable to power the lamp and motor of a scanner from the 500mA that can be supplied by USB whether via the motherboard or a hub and any that do this are liable to cause damage to the motherboard. Many external modems also have independent power supply units. So, anything requiring more than the 500mA available from each USB port will have its own power source. The computer system is designed to be able to cope with this.

Don't be misled about the current available from a motherboard. Just because the power comes from a copper track laid down on a piece of plastic sheet rather than from a cable doesn't mean it is somehow weak and feeble.


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