XPost: comp.os.ms-windows.misc, alt.comp.os.windows-7, alt.windows7.general   
   From: G6JPG@255soft.uk   
      
   On 2025/8/16 15:2:31, NY wrote:   
      
   []   
      
   > I have had problems with bus-powered USB devices that are powered by a   
   > USB hub rather than by the computer.   
   >   
   > The general advice with the Raspberry Pi (so not Win 7!) is that   
   > bus-powered spinning hard disks should be powered by a USB hub with its   
   > own power-supply rather than from the Pi itself. This worked find for   
   > the Pi 3, but when I got a Pi 4, I found that it failed to boot (not   
   > even any output on HDMI so no diagnostic message) if the powered hub had   
   > power. If the hub was unpowered, the Pi booted but (as expected) failed   
   > to see the external drive. If I booted the Pi and then turned on the USB   
   > hub, I could manually mount the drive.   
   >   
   > Some people suggested that there was a conflict between the Pi's power   
   > through the USB port and the external power to the hub. I made up a USB   
   > cable with the +5V line cut. This made no difference to the booting   
   > problem. It did still allow the drive to communicate as long as the   
   > power to the hub was off at boot time and only later turned on.   
   >   
   > I had to resort to a powered caddy and no powered USB hub. That works   
   > flawlessly.   
   >   
   > So powered USB devices can be a pain.   
      
   I have had PCs that wouldn't boot if a USB memory stick was plugged in.   
   I can't remember whether it was any memory stick in any port, or just   
   certain sticks, or certain ports. It would have been, I'm pretty sure,   
   either Windows 7 or XP (USB under Windows 9x was pretty flaky anyway). I   
   haven't had that problem with this W10-64 machine, but possibly only   
   because I've never tried booting it with a stick plugged in so far.   
      
   Yours is interesting: it saw the hub if unpowered. Presumably it was a   
   hub that could be either externally powered or bus powered (but of   
   course couldn't power a high-load peripheral if only bus-powered). My   
   guess was that its internal processor (or registers, or whatever) went   
   to - or at least ended up in - a different state if external power was   
   applied before communication commenced.   
   --   
   J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf   
      
   Self Test for Paranoia:  You know you have it when you can't think of   
   anything that's your own fault.   
   - "The Real Bev" in comp.mobile.android, 2019-1-1   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)