Sunday, July 10, 2011

USB Devices Dropping Out?

If you have a situation where USB devices suddenly quit working and become unrecognizable, then the issue is POWER. With USB 2 and 3 devices want 4.5 watts of power each. That is how thumb drives, hard drives, and phones get recharged over USB. Yes, it is amazing that hard drives can run on so little power, but that is beside the point.

Sometimes you've got too many devices plugged in, and the power causes one or more to 'drop out'. I've had the controller itself even become non-functional until a reboot.

On my PC, I fixed this long-standing issue by raising the SB voltage 0.1 volts (to 1.6) and going to the vendor supplied USB driver. I am not for sure which made the real difference, but I suspect the SB voltage increase.

USB Drop Out Notes:
  1. Get the latest proper driver from your motherboard (or USB PCI card) manufacturer to be sure. Windows probably has one that is fine in its database, but you never know. It takes time for WHM drive certification, so bugs could have been fixed since the last one pushed out by Microsoft.
  2. Increase your SouthBridge (SB) power a little. Don't blow it out of the water, but increase it some. Most enthusiasts motherboards have this setting in the BIOS.
  3. If you are using an external hub, make sure it has a separate power supply. Without it, there is no way it can take a single USB port's power and divide it so many times without some risk of a device not getting enough power.
  4. If you are overclocking, you may wish to lower your primary (HT, FSB) bus speed to its default. Just try. Make sure that is not the issue.
  5. Some devices can actually overheat and malfunction themselves if put through too much strain. Thumb drives, for instance, can get surprisingly hot if you really put them through the wringer. Whether or not this could ever cause them to quit functioning until they cool down, I don't know. The tolerance is probably very high.
General USB Performance Notes (while on related subject):
  1. Be aware that on many computers right now only a portion of the USB slots are USB 3.0. Find out which ones. On my PC, they put the USB 3.0 ones on the front, and the rest are USB 2.0. Strange, I thought, but whatever. Of course, if your device isn't USB 3.0 compliant, it won't matter anyway. USB 3.0 is a huge leap in bandwidth, so is worth it. Since all manufacturers with high-bandwidth needs are adopting it, it does not even cost the consumer more. In short, USB 3.0 is one upgrade that will really matter to home consumers.
  2. Going through additional hubs can degrade your throughput. You wouldn't think it would, but it does for whatever reason. Maybe I buy cheap hubs.
  3. Fortunately the USB interface was designed to allow real-time devices like keyboards and mice to get their data through as quickly as possible, so don't worry so much about whether they are on a secondary hub or not.
  4. Surprisingly, some USB 2.0 thumb drives (and other devices?) seem to perform MUCH faster when plugged into USB 3.0 ports. Yes, I am not sure what to make of it either. Maybe the Sandisk Cruzer 16GB drive I have supported USB 3.0 before it was marketed as such, or supported some early draft -- I don't know. I do know this baby 'books it' on a USB 3 slot... I mean, not a little faster, orders of magnitude faster (bandwidth wise, probably little change in latency).

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