Stephen Conrad wrote: > So, I plugged in (via USB) my USB Hub and I plugged in 2 USB Thumb > Drives (a 2 GB and a 247 MB one (according to the Get Info command) > but when I tried to plug in a 3rd (512 MB drive) it gave me a Low > Power Warning. > Now, it will take a 5V DC power cord and then I can switch it from > bus-powered to self-powered. However, the folks at Rat Shack (Radio > Shack) said it can run off the USB bus and I can use it with 4 thumb > drives.
Rule one (in any list of rules, anywhere): DON'T listen to anyone at Radio Shack. You CAN use four flash drives off of a hub IF all four flash drives use a maximum of 100mA. That is they report a maximum current draw of 100mA. Background: USB devices when connected automatically get 100mA allocated to them. Upon communicating with the computer a device may request more current, in 100mA steps, up to 500mA max. This is subject to available current. When in self powered mode there is a total of 500mA for the hub and any devices plugged in to it. The hub itself takes 100mA leaving 400mA for the rest. So if each of four devices plugged in to a self powered hub only requests 100mA then they can all be used. But if one or more requests more current then it won't allow more devices to operate. When using external power (a wall wart) the hub can typically power all devices at the full 500mA capacity. Now here is the rub... some USB devices request 500mA regardless of how much power they actually need. I suspect this is because the programmers of the code in the USB device left the current setting at a default value, never setting it to what is actually needed for their product. You can find out how much each device is requesting by looking under the USB section in Apple System Profiler. > > PS.....I emailed Fastmail.fm about my issue and will let you know what they > say. > And Fastmail is??? -- Clark Martin Redwood City, CA, USA Macintosh / Internet Consulting "I'm a designated driver on the Information Super Highway" --~--~---------~--~----~------------~-------~--~----~ You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list -~----------~----~----~----~------~----~------~--~---
