USB port doesn't have enough power / voltage / amperage?


Apr 9, 2009
I have a Cosmos S case, with 4 USB ports on the front panel and 4 on my motherboard round the back.

Since I build this computer, I have not been able to write more than a few MB's of data to either a flash stick or external drive without it crashing. My computer will freeze up, and all USB devices will not work (including my mouse ¬__¬).

If I check in my computer, my two external drives are still shown, but I can't access them. If I remove them, the icons still stay in my computer.. and if I insert them into a new port a NEW icon is shown (so I have two for a single device) but I can't access either.

I need to restart my computer to get things working normally again.

Small files which transfer fast, no problem.. I can do that with ease on the front and back ports. And some large files transfer okay to my external drives which are plugged into the motherboard. But anything over 200MB is very iffy and will have a 50/50 chance of causing this error.

This is obviously painfully annoying; having two 500GB external drives with I can't write to.. They are ment to be backup drives and at the moment haven't been backed up to for weeks.

It makes no difference if I turn off my external drives, then try to use the front panel.. I still crash even on files as small as 10MB.

I posted this else where and was told that it sounds like my ports don't have enough juice.. which is why I can read and delete items.. but when writing it takes more power.. and causes a crash.

Has anyone ever come across this?
Any idea how I can solve this?

I've got a right mind just to pop these externals into the computer and run them there.. it means I can't use them as portable storage but I need backups for my business.

Any help would be great.


Apr 10, 2009
what kind of externals are they.

if they are usb powered (2.5" laptop drive) then you can only plug one in at a time.

also try to put all the unpowered devices on the other usb set.

Keyboard mouse etc all on back of computer.
1 backup drive only on front usb

you could actually try that even if you have a 3.5" external drive with a transformer.

you could also try buying a self powered usb hub with external transformer.

or a usb add-on card. both should be under 20$

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