Re: Boot from USB on RPi4 8GB?

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.



> 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 @ 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)