Date: Mon, 20 Dec 2021 08:39:34 +1100 From: MJ <mafsys1234@gmail.com> To: bob prohaska <fbsd@www.zefox.net> Cc: freebsd-arm@freebsd.org Subject: Re: Dealing with slow USB disks, was: Re: Saving environment variables in u-boot Message-ID: <6edfdb4a-8ed3-7ef3-c3b2-7d2d7fd3206c@gmail.com> In-Reply-To: <20211219161816.GA14873@www.zefox.net> References: <20211217013613.GA4452@www.zefox.net> <E2F6D50B-694A-4108-BD84-C85BC96AD832@yahoo.com> <20211218005946.GA7670@www.zefox.net> <5C44D0E6-2FF1-4EEB-B21A-83333D6FCF46@yahoo.com> <9D416106-660F-40BB-98D2-1354B53D2FEF@yahoo.com> <EC6CC83C-BC0A-4A12-866A-9FA24083FF7E@yahoo.com> <20211218223543.GA9484@www.zefox.net> <6105a8a6-e760-2183-72fd-92e5a60aa8df@gmail.com> <20211219005134.GA12292@www.zefox.net> <4910504f-3051-9a95-d8e4-95434042196d@gmail.com> <20211219161816.GA14873@www.zefox.net>
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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
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