I don't have the Plan9 uSD card handy, but to the best of my recollection all Raspberry Pi SD cards have at least two partitions on them. The ARM processor remains halted upon reset and the VideoCore loads the image from the (first?) DOS formatted partition. Once that image is loaded into RAM, the ARM processor starts running it.

I'm not even sure that uboot is involved.

You might find some useful information at: http://raspberrypi.stackexchange.com/questions/10489/how-does-raspberry-pi-boot

Whilst the details are for Linux, I assume that Plan9 booting is very similar.

On 24 October 2015 at 08:25, Adriano Verardo <adriano.verardo@mail.com> wrote:

I'm using a rpi with prof Miller Plan9 img.
A remarkable work.
I would like to know the details of the rpi boot process.
i.e. where u-boot is stored, how to generate a micro sd etc.
After reading some doc, I'm getting a bit confused.
Could someone kindly indicate a "roadmap" and some good doc ?

Thanks in advance

adriano