Boot from second SD card (SD1 pins)

[romanjaloza]

Is there any possibility to boot from second SD card interface (SD1 pins, ALT3 RPi 1.2 B+)?

It means that I need to use build-in SD card slot for user data access and add a second SD card slot adapter for start.elf, bootcode.bin, /boot/config.txt and OS files.

Unfortunately GPU code is not open source and there is no information about the first stage bootloader rules.
Will the GPU code detect cards from both interfaces SD0 and SD1? or only direct access to SD0 is implemented.

Best Regards,
Roman

[Navyscourge]

Where did you get the idea you can use 2 SD cards (SD1)?

The Pi boots from the card in the SD card slot. It can be configured to boot from a USB hard drive, or another SD card in a USB holder. A SD card in a USB holder can also be used as a data storage location

[fruitoftheloom]

NO

viewtopic.php?f=98&t=108585

viewtopic.php?f=44&t=72671

[romanjaloza]

Where did you get the idea you can use 2 SD cards (SD1)?

As it was mentioned, I was wondering is it possible.

The Pi boots from the card in the SD card slot. It can be configured to boot from a USB hard drive, or another SD card in a USB holder. A SD card in a USB holder can also be used as a data storage location

Thanks, these configurations are quite obvious, that is why my question was related with first stage bootloader implementation.

[romanjaloza]

NO

viewtopic.php?f=98&t=108585

viewtopic.php?f=44&t=72671

Thanks, for these links. I've made research but these ones are new for me.

[W. H. Heydt]

The Pi boots from the card in the SD card slot. It can be configured to boot from a USB hard drive, or another SD card in a USB holder. A SD card in a USB holder can also be used as a data storage location

Say, what? A Pi boots from an SD card. Period. You can have the root partition for the system on another device, but the Pi still boots from the SD card.

[romanjaloza]

The Pi boots from the card in the SD card slot. It can be configured to boot from a USB hard drive, or another SD card in a USB holder. A SD card in a USB holder can also be used as a data storage location

Say, what? A Pi boots from an SD card. Period. You can have the root partition for the system on another device, but the Pi still boots from the SD card.

Yes, that is the truth.
The idea of selective boot from on-board SD card and second SD1 interface was already mentioned in other discussion, but it is not implemented now.

My idea was to prepare RPi shield with power supply, communication part and second SD card interface to hide system SD card and protect against damage.
My second interface is accessible by SPI bus now, but it is not possible to use it as a "bootable disk"

[fruitoftheloom]

Yes for completeness the VPU (VideoCore IV) Boots the Raspberry Pi and seeks the Boot Files, Configuration Files and Kernel on SD0 Card (except the Compute Module which has an eMMC instead of a SD Card),

http://wiki.beyondlogic.org/index.php?t ... ot_Process

[kirgene]

Here is interesting info about boot from secondary SD:

...
If enabled: check secondary SD
Success - Boot
Fail - timeout (five seconds)
...

The primary SD card boot mode is, as standard, set to be GPIOs 49-53. It is possible to boot from the secondary SD card on a second set of pins, i.e. to add a secondary SD card to the GPIO pins. However, we have not yet enabled this ability.

[W. H. Heydt]

Here is interesting info about boot from secondary SD:

...
If enabled: check secondary SD
Success - Boot
Fail - timeout (five seconds)
...

The primary SD card boot mode is, as standard, set to be GPIOs 49-53. It is possible to boot from the secondary SD card on a second set of pins, i.e. to add a secondary SD card to the GPIO pins. However, we have not yet enabled this ability.

That would also require that the pins for SD1 be exposed. I don't know, one way or the other, if they are. If anything has a good chance to expose them, it would be the CM-series Pis.