Date: Sun, 30 May 2021 13:50:16 -0700 From: Mark Millard via freebsd-arm <freebsd-arm@freebsd.org> To: freebsd@dsllsn.net Cc: freebsd-arm@freebsd.org Subject: Re: Boot from USB on RPi4 8GB? Message-ID: <D82CA5FE-1755-4D38-928E-B8234A4F38D4@yahoo.com> In-Reply-To: <2F58272B-BD9C-464B-9A98-BF638971BA86@dsllsn.net> References: <4F3EE8D2-649B-4522-AD5A-7C308291802F@dsllsn.net> <43FAEEAC-EE36-4810-88AA-FF82AFBCC128@yahoo.com> <2F58272B-BD9C-464B-9A98-BF638971BA86@dsllsn.net>
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On 2021-May-30, at 10:59, William Carson via freebsd-arm <freebsd-arm at = freebsd.org> wrote: >> . . . >> I use a USB3 SSD that has small enough power requirements >> to not require a powered hub. (I also use a 5.1V 3.5A >> power supply as part of that context.) I've never tried >> spinning rust or higher powered USB3 media. I view the power supply that I use as just giving a little more margin, not as a way to increase what the devices total to. > . . . I'm not sure what's considered "high powered" but the Samsung = tech specs say this particular model uses 5.7 W on average and 10.0 W = maximum. But it does seem curious that the Raspberry PI OS will boot = this disk without issue, so I don't think it's the drive. I also tried a = Samsung 950 PRO using a different enclosure (QNINE NVME Enclosure, M.2 = PCIe SSD (M Key) to USB 3.0 External Case), but it behaved the same. . . . Then you need to use a powered hub for that device. = https://www.raspberrypi.org/documentation/hardware/raspberrypi/power/READM= E.md lists: "Maximum total USB peripheral current draw" as: 1.2A , which at 5.1V is 6W. That figure is the total for all USB devices attached that are not powered independently. That document also says that a 5.1V supply is required, not 5V. The power supply that the RPi folks supply is 5.1V @ 3A or 15.3W. Even the 5.1V 3.5A power supply that I use only multiplies out to 17.85W. =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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