Re: Boot from USB on RPi4 8GB?

From: William Carson via freebsd-arm <freebsd-arm_at_freebsd.org>
Date: Sun, 30 May 2021 18:54:29 -0500
> On May 30, 2021, at 4:08 PM, Mark Millard <marklmi_at_yahoo.com> wrote:
> 
> On 2021-May-30, at 13:50, Mark Millard via freebsd-arm <freebsd-arm at freebsd.org> wrote:
> 
>> 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.
> 
> I should have just referred to independent power. You
> had written:
> 
> QUOTE
> I'm trying to use a SAMSUNG (MZ-V7E500BW) 970 EVO SSD 500GB - M.2 NVMe, attached via the Geekworm X872 M.2 NVMe 2280/2260/2242/2230 SSD Expansion Board.
> END QUOTE
> 
> https://geekworm.com/products/raspberry-pi-4-x872-m-2-nvme-2280-2260-2242-2230-ssd-expansion-board
> 
> shows that it has its own power connector and has an image
> that says "please power x872 via DC Jack of XH2.54 connector
> if SSD is not recognized or low power". Later text on the
> page says:
> 
> QUOTE
> Specifications:
> Power Supply
> 	• 5Vdc +/-5% , Powered by Raspberry Pi USB port
> 	• 5Vdc via DC power jack or XH2.5 connector, Extra power for the SSD
> END QUOTE
> 
> So, if I gather right, you need to connect a power
> supply to the X872 and another to the RPi4B.
> 
> Another image says "Note: NOT recommended to use SAMSUNG SSD,
> if use SAMSUNG SSD, please close WiFi". Later text on the page
> says the same.

A-ha, indeed. I just noticed that as well. I've gone ahead and ordered a supplementary power supply and a lower-power NVMe to do more testing. I'll send an update once I've received and tested them.

Thank you for hopefully pointing me in the right direction.

> https://www.raspberrypi.org/documentation/hardware/raspberrypi/power/README.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 _at_ 3A
>> or 15.3W. Even the 5.1V 3.5A power supply that I use
>> only multiplies out to 17.85W.
> 
> ===
> Mark Millard
> marklmi at yahoo.com
> ( dsl-only.net went
> away in early 2018-Mar)
> 
> 
> 
> ===
> Mark Millard
> marklmi at yahoo.com
> ( dsl-only.net went
> away in early 2018-Mar)
> 
Received on Sun May 30 2021 - 23:54:29 UTC

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