How to tell Risc OS which is the ADFS(Filecore) partition it has to use?

Hi!

As you may know, Risc OS is not available in NOOBS for the Pi4, but it works very well on the Pi4 anyway.

SO, I am trying to install it in an SD along with other NOOBS-installed OSes.

I can easily copy over the FAT16 PiBoot and ADFS partitions to a multi-boot SD card built with noobs (I use GPARTED to copy the partitions over to the NOOBS sd), and I can easily create an entry for Risc OS in SETTINGS/installed_os.json
Doing it, Risc OS DOES boot from the NOOBS menu after I manually copy over it’s partitions and create the entry for it on the menu, BUT it leaves me in the SUPERVISOR prompt instead of taking me to the desktop.

My guess here is that Risc OS can’t find the ADFS/FileCore partition on the card. How can I tell Risc OS what ADFS/FileCore partition to use?
I am almost there! Stuck on the SUPERVISOR but my forced istallation boots! Help! :D

EDIT: Maybe Risc OS is stuck on the SUPERVISOR prompt because it will only load the CMOS settings file from one given partition? Ok, then, how can I change that?

The short answer is: RISC OS doesn’t understand partitions. It expects the Filecore “partition” to be at the start of the SD card, so if you’re trying to add it to a card which already has other OS partitions, it’ll end up in the wrong place.

What might work is to start with RISC OS installed via NOOBS and then add other (NOOBS-installed) partitions to that SD card.

EDIT: I suspect even that won’t work. IIRC there can be only one “boot” partition, and RISC OS’s boot partition is… special. NOOBS could try to move (or even overwrite) that partition, with unfortunate knock-on effects.

This is not a direct answer to the original question,

But, looking at your previous posts, I think you will be able to do the following as a work around to complete your multiboot system:-

Copy your RISCOS filecore data to a Filecore formatted memory stick and put the memory stick in an empty USB port on the Pi. Then,
Whilst at your current RiscOS supervisor prompt, type
*configure filesystem SCSI
*configure SCSIFSdrive 4

and then reboot.

@Bryan That would need the USB stick necessary for booting Risc OS always, right?

@Painting: maybe the best solution would be to FORCE installation of Risc OS on the Pi4 from NOOBS.
But is that possible at all?

maybe the best solution would be to FORCE installation of Risc OS on the Pi4 from NOOBS. But is that possible at all?

Not at the moment, no. When RISC OS 5.28 is released, a NOOBS install should work on the Pi 4. Hopefully you won’t have long to wait :-)

Well then, I will have to wait for 5.28 then, or no multiboot for me… Thanks! :)

The short answer is: RISC OS doesn’t understand partitions. I

Fortunately RISC OS filecore partition starts at a point just beyond where the partition table is stored (it ignores what is stored in the partition table). The filecore bit knows its own length from inside itself.

That means you can make an entry in the partition table that exactly corresponds to the space the filecore partition uses (and another entry which corresponds to an overlap of a FAT partition and the location in the filecore bit where the !Boot.Loader DOS image file resides).

Now you can add a partition that can reside in the space on the SD card that is not yet marked as used.

So the answer to your question – how does RISC OS know where the filecore disc image resides – it is at a fixed address offset from the start of the card.