Re: Dealing with slow USB disks, was: Re: Saving environment variables in u-boot
Date: Sun, 19 Dec 2021 21:39:34 UTC
On 20/12/2021 3:18 am, bob prohaska wrote: > On Sun, Dec 19, 2021 at 10:03:47PM +1100, MJ wrote: >> >> I would think a mechanical USB is going to pull a "lot" of power when beginning spin-up, but once rotating should be easily powered by a USB hub. Though this would not explain how it works on RPI4 unless the powered hub you're using is USB2. >> > > That's what I thought too. I certainly didn't expect the disk to work > without a powered hub. The Pi4 is a different animal; it has USB3 ports > and more power available. That the mechanical disk works at all on the > Pi3's USB2 ports without assistance is quite surprising. See here: https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#typical-power-requirements It mentions 1.2A, which covers your load, but, I would suspect if you attached, for example, a USB 'thumb' drive or other devices you would cause problems. > > There's a table at > https://hddfaqs.com/seagate-st1000lm048/ > listing power requirements for the drive: > Required Power For Spinup: 1000 mA > Power Required (Seek): 1.7 W > Power Required (Idle): 1.6 W > Power Required (Standby): 0.18 W The total draw capable will inevitably come down to the power supply unless, as you know, you use a powered hub (and even then, it depends on the hub's power output abilities). M