Date: Sun, 19 Dec 2021 09:11:26 -0800 From: Mark Millard via freebsd-arm <freebsd-arm@freebsd.org> To: bob prohaska <fbsd@www.zefox.net> Cc: MJ <mafsys1234@gmail.com>, freebsd-arm@freebsd.org Subject: Re: Dealing with slow USB disks, was: Re: Saving environment variables in u-boot Message-ID: <3F624D6C-1A78-4F08-8AF2-A3959476F86F@yahoo.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 2021-Dec-19, at 08:18, bob prohaska <fbsd@www.zefox.net> wrote: > On Sun, Dec 19, 2021 at 10:03:47PM +1100, MJ wrote: >>=20 >> 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. >>=20 >=20 > 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=20= > Pi3's USB2 ports without assistance is quite surprising.=20 >=20 > There's a table at > https://hddfaqs.com/seagate-st1000lm048/ > listing power requirements for the drive: > Required Power For Spinup: 1000 mA (I'm guessing they list that as the largest surge current. But they do not list figures for READ or WRITE activity.) = https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#typi= cal-power-requirements lists the "Maximum total USB peripheral current draw" as: 1.2A (so 1200 mA) for the B+, 2B, 3B, 3B+, 4B, and Pi400. The 3B and 3B+ list a "Recommended PSU current capacity" of 2.5A, the 4B lists 3.0A. Some keyboards or other such could lead to problems if also connected at power up: Having both a keyboard and mouse at power up, in addition to the drive, could be a problem: QUOTE keyboards and mice can take as little as 100mA or as much as 1000mA END QUOTE So stick to a low total power for your other USB devices that are to be already connected at power up. You might have to carefully pick what keyboards/mice/whatever to fit the 200mA budget that is left --or plug some things in only after the drive has spun up. > Power Required (Seek): 1.7 W > Power Required (Idle): 1.6 W > Power Required (Standby): 0.18 W >=20 > So far I haven't tried to power cycle the combo, that might not work.=20= > Still, it's been an informative exercise. Getting rid of the hub is a > welcome simplification. The machine is still up after standing = overnight. =3D=3D=3D Mark Millard marklmi at yahoo.com
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