Raspberry Pi 400

I reckon I’ve identified your problem

I reckon you have. SD card is now present after USB boot.

Thanks very much.

Starting up the update 14 ROM on a USB stick and with no SD card in the slot the boot stops at a command prompt.

Correct. The CMOS file specifies SDFS as boot filesystem.

Insert a card enter the desktop and clicking on the SD card icon results in the “The disc drive is empty” message.

Problem.

It’s an ex-problem now. Fixed in git.

don’t know if this is related but on my pi4 booting from usb if i have an sdcard running fat32fs in the slot it will not see the adfs formated part of the drive only the fat part so i stopped loading fat32fs so that you can see adfs when the system has started.

don’t know if this is related but on my pi4 booting from usb if i have an sdcard running fat32fs in the slot it will not see the adfs formated part of the drive only the fat part so i stopped loading fat32fs so that you can see adfs when the system has started.

Try right click to get the filecore partition. Fat32fs picks up the FAT partition automatically when left clicking for SCSI but not for SDFS.

I reckon I’ve identified your problem

Thanks from me too.

The only other quirks from booting from just USB is the CMOS file is not updated automatically. Would also be handy to have a failover boot filesystem (to SCSI) if no SD card is present.

RISC OS Direct is a bit out of date. Specifically it is missing an ‘Autosense’ file that detects the presence of the EtherGENET interface. Updating !Boot should sort that out.

This was it – in case it helps anyone else, I updated !Boot with the version from the HardDisk4 nightly. Thanks again to everyone for your help.

After lots of faffing about, it seems that the presence of the file ‘bcm-2711-rpi-4-b/dtb’ in the FAT partition will stop RISC OS starting up on the Pi 400 (but it is fine on the Pi 4). Otherwise RISC OS starts up fine with the 5.29 (14-Nov-2020) rom from Update 14 (revised today) and the CONFIG/TXT and CMDLINE/TXT files as below. With the offending file replaced again (and with ‘kernel8/img’ there as well) it all works on the Pi 4. It will boot into RasPiOS with the switch on the header closed and into RISC OS with it open. Put the same card into the Pi 400 and it will boot into RaspiOS with the switch held down but the presence of the file ‘bcm-2711-rpi-4-b/dtb’ prevents it booting into RISC OS when the switch is left open (delete that file and RISC OS starts up OK on the Pi400 but RasPiOS just stops at the multi-coloured square and flashes the LED seven times [when tried on the Pi 4]).

Nothing seems to call for this file in CONFIG/TXT or CMDLINE/TXT which contain the following (note the UUID refers to the ext4 partition on the USB pen drive which has the Raspian disto on it):

CMDLINE/TXT:
disable_gamma console=serial0,115200 console=tty1 root=PARTUUID=00bcf131-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles
CONFIG/TXT:
[gpio5=1]
fake_vsync_isr=1
framebuffer_swap=0
gpu_mem=64
init_emmc_clock=100000000
ramfsfile=CMOS
ramfsaddr=0x508000
kernel=RISCOS.IMG
[pi4]
enable_gic=1
[all]
[gpio5=0]
# Enable audio (loads snd_bcm2835)
#dtparam=audio=on

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

[all]
#dtoverlay=vc4-fkms-v3d

Can anyone shed light onto this please? It looks like something that will need Ben’s input.

Latest official Beta ROM build (15.11.2020) works on my Pi 4 and Pi 400 :-). Pi 4 booting from SD, Pi 400 from SSD. Thanks a lot, also for the inofficial ones.

Latest official Beta ROM build (15.11.2020) works on my Pi 4 and Pi 400

Yes, me too – I had built the rom before the source changes were merged.

The problem above arises when adding some extra files to the FAT partition. It is not CMDLINE/TXT causing the file to be loaded and the EEPROM firmware is the same on both machines. So it is some subtlety of the Pi 400 that is causing the issue.

So it is some subtlety of the Pi 400 that is causing the issue.

After a lot of thinking and reading it appears that the default device tree (bcm2711-rpi-4-b/dtb) which is loaded (if present) and passed to the kernel (with any ramfs (a.k.a. CMOS), memory configuration and command line string data substituted) as an alternative to filling memory from 0×100 with ATAG data causes no difficulty on a Pi 4. Device Tree and ATAGs are mutually exclusive, and passing a DT blob to a kernel that doesn’t understand it will cause a boot failure. On a Pi 400 this is what happpens. The firmware will always try to load the DT (if it is present in the FAT partition) and pass it to the kernel.

To solve this, add the command ‘device_tree=’ to the conditional part of config.txt that applies to RISC OS.

Now it all works:

The latest beta RPi 4 bootloader now has filters for the RPi 400 and CM4. See here.

After a bit of experimenting the RPi4 400 runs stable at 2.4GHz with,

[pi400]
arm_freq=2400
over_voltage=10

for the 8GB RPi runs stable at 2.2GHz (Needs active colling).

[pi4]
arm_freq=2200
over_voltage=8

As ever use at your own risk. Stable on both here for the last few weeks.

Do we have a step-by-step guide for getting RISC OS to work on the 400?

Do we have a step-by-step guide for getting RISC OS to work on the 400?

Download the stable RISC OS 5.28 SD card image and then download a daily development RISC OS 5.29 ROM (which since 15 Nov has supported Pi 400). Err that’s it.

Do we have a step-by-step guide for getting RISC OS to work on the 400?

Try this one.

Thanks. I’m not sure how I managed to miss that.

Hi. I’m new to all of this, more or less. Will the ePic card work in the Pi 400?

Will the ePic card work in the Pi 400?

To update a recent ePic card (October 2020 or later) for the Pi 400:

• Download the latest Beta RPi ROM (BCM2835Dev) archive from the Downloads page. Unpack this to retrieve the riscos.img file.
• Download the latest versions of fixup4.dat and start4.elf from the Raspberry Pi firmware page.¹
• Replace the riscos.img, fixup4.dat and start4.elf files in the FAT16 partition of the ePic card.
• Dismount the card before unplugging it.

N.B. If you have an older ePic card (i.e. if riscos.img has a datestamp older than October 2020) this won’t work.

¹ For each file, click through until you get an actual Download button.

Sounds easy enough. Thank you Stuart!

I’m also interested in using ePic on a Pi 400 – because I’d like to support ROOL and experience the wide range of software on offer. Is it still necessary to use the beta release of the ROM or can the stable version 5.28 be used now? I ask because the disk image for the Pi 400 is v5.28, released around the time of the last post.

For that matter, maybe someone could clear up what the difference is between the Pi 400 disk image and the “normal” version… Is the v5.28 disk image for Pi 400 patched, and v5.29 beta is the first “universal” version? In that case I guess I still need to use the beta if I want to combine it with ePic.

The Pi 400 image is effectively 5.28 with extra drivers to make it work on the Pi 400. It’s only supported for use on the 400: It also works on my 4, but I suspect that ROOL didn’t want to go to the trouble of fully testing everything so slapped an “only for 400” label on it.

I’m not sure about ePic. Its previous incarnation, NutPi, included a tool to ‘merge’ the software with a different SD card but I don’t know whether this is still practical with ePic.