Re: Dealing with slow USB disks, was: Re: Saving environment variables in u-boot

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