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Sun, 19 Dec 2021 15:48:44 -0800 (PST) Received: from [192.168.1.10] ([115.69.53.183]) by smtp.gmail.com with ESMTPSA id u22sm15898401pfi.187.2021.12.19.15.48.43 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 19 Dec 2021 15:48:44 -0800 (PST) Subject: Re: Dealing with slow USB disks, was: Re: Saving environment variables in u-boot Cc: freebsd-arm@freebsd.org References: <20211217013613.GA4452@www.zefox.net> <20211218005946.GA7670@www.zefox.net> <5C44D0E6-2FF1-4EEB-B21A-83333D6FCF46@yahoo.com> <9D416106-660F-40BB-98D2-1354B53D2FEF@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> <6edfdb4a-8ed3-7ef3-c3b2-7d2d7fd3206c@gmail.com> <1387CAB3-CFE7-4C47-8A9C-24D6E56D8C3C@yahoo.com> From: MJ Message-ID: Date: Mon, 20 Dec 2021 10:48:38 +1100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 List-Id: Porting FreeBSD to ARM processors List-Archive: https://lists.freebsd.org/archives/freebsd-arm List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-arm@freebsd.org MIME-Version: 1.0 In-Reply-To: <1387CAB3-CFE7-4C47-8A9C-24D6E56D8C3C@yahoo.com> Content-Type: text/plain; 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FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-arm@freebsd.org]; NEURAL_SPAM_MEDIUM(1.00)[1.000]; RCPT_COUNT_ONE(0.00)[1]; NEURAL_SPAM_LONG(0.99)[0.990]; RCVD_IN_DNSWL_NONE(0.00)[2607:f8b0:4864:20::535:from]; RCVD_TLS_ALL(0.00)[] X-ThisMailContainsUnwantedMimeParts: N Status: O Content-Length: 1749 Lines: 35 On 20/12/2021 9:55 am, Mark Millard wrote: > On 2021-Dec-19, at 13:39, MJ wrote: > >> 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. > > Unfortunately there is more involved: USB2's standard > indicates 500mA (0.5A) at maximum on 1 standard USB2 > port. It takes 2 USB2 ports to get to a total of 1000mA > (1A) (unless a port is designed to go beyond the > standard). To my knowledge most RPi*'s are not designed > to support more than the standard USB2 power on any of > its USB2 ports. (The 3A+, Zero W/WH, and Zero are > apparently exceptions, depending on the power supply > used and such.) You are correct, however, it seems the RPI foundation violates the "standard" and creates their own for Bs: https://raspberrypi.stackexchange.com/questions/51615/raspberry-pi-power-limitations (Section: How much current can be drawn from the USB ports?) M