Is there limit on # of USB devices into 1 port?

By drpepper55
Sep 30, 2008
  1. Hi all, I have a Dell Latitude CPX650 w/XP Home. My Dell has only 1 USB port in the back, it being of the 1.1 variety but I have been able to use 2.0 hardware to it and they have been compatible w/no problems for 3 years plus. I added a 4-port USB hub and have for the most part used 3 of those ports pretty much all of the time-and occasionally all 4- into my 1 on the back of the Dell for over 1-1/2 years now and also have had no problems. I bought a chill pad here recently that came with a built in 4-port hub in the base. If I connect the 4-port into 1 of the ports on the first 4-port hub, should I expect problems? Is there a rule of thumb or a common practice into how many ports can be extended from or put into 1 port? Thanks guys...
  2. jobeard

    jobeard TS Ambassador Posts: 9,160   +599

    The issue is POWER consumption. Each port is limited to 500ma current draw.
    Using a USB hub that has its own power source can escape that limit.

    The usual devices that cause problems are Ext HDs (should be obvious; more power to spin the platters).

    All USB 2.0 devices are downward compatible to 1.1
  3. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,689   +395

    127 is the max.
  4. drpepper55

    drpepper55 TS Member Topic Starter Posts: 65

    Thanks jobeard and SNGX for the replies. This answers my questions and allays my worries about pushing my luck too far. As it is, I use 3 of my ports as I said most of the time and they are for my wireless mouse's receiver stick and for 2 external hdds but they have their own power source for running the drives so I don't believe any power is expended from my port to run those. Now the other 4 ports I added via the chill pad also have their own power source but the 1st 4-port hub was unpowered. Because of this I have changed and made my powered 4- port hub on the chill pad as my main hub and the unpowered 4-port hub as an extension of 1 of my powered ports for when I need extra input ports for additional devices, if and when I need them. For most of my uses 4 ports does me fine, so I believe I should be ok. Thanks again, best to you...
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