Re: Homebrew pi400

Theo <theom+news@chiark.greenend.org.uk> wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 11/12/2024 16:46, Daniel wrote:

Andy Burns <usenet@andyburns.uk> writes:
 

Daniel wrote:
>

Jeff did a teardown on his second channel and soldered a m.2 socket
hoping it was properly designed. He found the power lines weren't traced
in so no power.

>
There were some nearby component missing too, maybe the Rev1 board has
bugs, and they need a Rev2 (or whatever) but his soldering job looked
relatively clumsy (bridged pins etc).

 
Yeah, it was pretty bad, at least he was honest about it.
 
I am sure things were missing to keep the circuitry disabled and I'm no
engineer.

 
Why would you put support chips on if you were not going to install an
M.2 socket anyway?
 
I think he called it right in that this is a bare bones model, and more
upmarket versions will emerge in due course.

 
Looking at:
https://www.jeffgeerling.com/sites/default/files/images/pi-500-m2-socket-install.jpg
https://www.jeffgeerling.com/sites/default/files/images/pi-500-pcb-bottom.jpeg
 
I think there's a MOSFET and some decoupling capacitors missing (to the left
of the middle larger hole), so the power isn't connected.  There may be a
pair of missing capacitors in series with the PCIe lane, but I can't
immediately see the footprints for those.

Ah, I see them now.  To the right of the spot on the silver chip are four
tiny spots for passives, oriented at compass bearing 135 degrees.  I can't
tell from the photo or video whether they're populated or not, but those
will be the series capacitors.

Theo