Pi Boot from USB?

Hi

I recently discovered that the more recent versions of the Raspberry Pi can boot from a USB drive. (with no SD card)

Does RISC OS support this?

The short answer is “Well, sort of…”

Updating the Pi’s Write-Once memory to allow “boot from USB” has to be done from Raspbian.

The USB boot drive needs to be set up in exactly the same way as the boot SD (i.e. with a FAT32 partition for the Pi boot loader, and the rest of the disc in Filecore format). SystemDisc should do this for you.

Where you might come unstuck are the CMOS RAM settings. RISC OS stores CMOS RAM settings on the boot SD: this is (a) hard-coded, and (b) not the same place that the Pi boot loader will be loading them from. You can (sort of) get round this by leaving the SD card plugged in and remembering to copy !Boot.Loader.CMOS to the USB drive every time you make a configuration change, but if your aim was to get rid of the SD card altogether this won’t fit the bill.

Where you might come unstuck are the CMOS RAM settings. RISC OS stores CMOS RAM settings on the boot SD: this is (a) hard-coded, and (b) not the same place that the Pi boot loader will be loading them from.

http://heyrick.ddns.net/files/SDCMOS.ffa
Save as “SDCMOS”, settype &FFA (Module).

It’s a copy of the standard SDCMOS with extra nulls added after the paths, so…

Load it into Zap, you’ll see this (some stuff above, some below):

00000048 : (15  : 20353128 : EORCSS  R3,R5,R8,LSR #2
0000004C : Oct  : 2074634F : RSBCSS  R6,R4,PC,ASR #6
00000050 : 2016 : 36313032 : Undefined instruction
00000054 : )... : 00000029 : ANDEQ   R0,R0,R9,LSR #32
00000058 : .... : 00000001 : ANDEQ   R0,R0,R1
0000005C : SDFS : 53464453 : MOVTPL  R4,#&6453
00000060 : :$.C : 432E243A : Undefined instruction
00000064 : MOS. : 00534F4D : SUBEQS  R4,R3,R13,ASR #30
00000068 : .... : 00000000 : ANDEQ   R0,R0,R0
0000006C : .... : 00000000 : ANDEQ   R0,R0,R0
00000070 : .... : 00000000 : ANDEQ   R0,R0,R0
00000074 : .... : 00000000 : ANDEQ   R0,R0,R0
00000078 : .... : 00000000 : ANDEQ   R0,R0,R0
0000007C : SDFS : 53464453 : MOVTPL  R4,#&6453
00000080 : :$.! : 212E243A : Undefined instruction
00000084 : Boot : 746F6F42 : STRVCBT R6,[PC],#-3906
00000088 : .Loa : 616F4C2E : Undefined instruction
0000008C : der. : 2E726564 : CDPCS   CP5,7,C6,C2,C4,3
00000090 : CMOS : 534F4D43 : MOVTPL  R4,#&FD43
00000094 : .... : 00000000 : ANDEQ   R0,R0,R0
00000098 : .... : 00000000 : ANDEQ   R0,R0,R0
0000009C : .... : 00000000 : ANDEQ   R0,R0,R0
000000A0 : .... : 00000000 : ANDEQ   R0,R0,R0
000000A4 : .... : 00000000 : ANDEQ   R0,R0,R0
000000A8 : .... : 00000000 : ANDEQ   R0,R0,R0
000000AC : Save : 65766153 : LDRVSB  R6,[R6,#-339]!
000000B0 : CMOS : 534F4D43 : MOVTPL  R4,#&FD43

Switch to ASCII mode (normally Sh-Ctrl-F1) and Overwrite mode (press Insert – title should say “(uao)” at the end).

Locate the first path (SDFS:$.CMOS) and change it as necessary within its limitations. Then do the same for the second path (the !Boot.Loader.CMOS one).

Switch back to Code mode (Sh-Ctrl-F5) and verify the second starts at offset &7C, and the SaveCMOS text starts at offset &AC. If they’re both good, save the module and then get it to load early in the boot sequence – an easy way is to drop the module into !Boot.Choices.Boot.PreDesk with an “!!” prefix. You’ll note that DeepKeys does exactly this.

If that looks scary, then… isn’t USB a SCSI device? If so, here’s an UNTESTED version with the “SDFS” replaced by “SCSI”. It might work.

http://heyrick.ddns.net/files/SDCMOSscsi.ffa

I recently discovered that the more recent versions of the Raspberry Pi can boot from a USB drive. (with no SD card) Does RISC OS support this?

It is a lot simpler to let the Pi boot from an SD card, but then to configure RISCOS to use a USB Drive. (*configure filesystem SCSI)

You do not then need either the SD card or the USB drive to be ‘partitioned’.

For best reliability use an SSD rather than a Flash memory stick.

Just reviving this as recently my SD card slot has become unusable. Is there no way to kickstart the boot from supervisor?

You should be able to just type,

*SCSI
*!Boot

Hi,

I am trying to get my RPi4 to boot RISC OS 5 from an external USB drive.

I have done lots of searching on various web forums to try and put together the correct process, which is kind of working.

I have:
> Updated the RPi4 BootLoader using Raspian.
> Configured the RPi4 BootLoader to boot from USB using Raspian.
> Installed “RISC OS 5 Direct” to my external USB SSD drive using the RPi Imager software on my Windows PC, as I have done with an SD card already, which worked fine. (Updated the firmware files as advised with the “RISC OS 5 Direct” download.)
> Booted the RPi4 from the USB, but it stopped at the Supervisor, with a keyboard error. (I have a cable USB keyboard plugged in!)
> *desktop
> Grey background with Error message that “the drive is empty”.
> Click cancel and the desktop loads with the “RISC OS 5 Development Ltd” logo.
> Warning that !Boot has not loaded.
> The iconbar shows the RISCOSPi drive which is a SCSI drive.
> I can open the drive and see the Boot folder, along with all the other main folders.

If I try to run !Boot, I get a message saying “the drive is empty”.
Is this because the RPi4 is looking for the CMOS on the SDFS SD drive, which is currently empty?
Is the USB FAT partition, which contains the firmware and CMOS files being seen at all on boot?

How do I make the changes to the USB config so that it can see the firmware and CMOS files on the USB?

I have tried to *configure the “filesystem to SCSI” and “SCSIFSdrive 4”. This returned no errors so I was hopeful that it was sorted, but a restart put me back in the same position.
I tried *SCSI, followed by *!Boot, but that gave me the error in the CLI that “the drive is empty”.

Any assistance that you can offer, as to what I should change to make this work, would be most welcomed.

Cheers,

Barry.

What are you trying to accomplish?

A. Free up the SD slot by not using an SD card at all, or
B. Use a USB SSD for increased storage and reliability, and forget the SD slot exists

If it’s B, then things are a bit easier to set up. You can store the ROM and CMOS on an SD card (which you can optionally hide the icon for), and use the USB SSD for everything else. I like this option because it works similarly to real Acorn hardware.

If you prefer option A then I believe it’s doable, but things are a bit more complicated, so can you please confirm which option you want to use?

I am trying to get my RPi4 to boot RISC OS 5 from an external USB drive.

The Pi ROM on startup reads CMOS from a file in the same folder as the Pi ROM image. The little catch is that the Pi ROM is hardwired to write CMOS settings only to SDFS locations. The necessary changes to have RISC OS start from USB are set but the the ROM attempts to write them to SDFS, the USB CMOS file is unaware of the changes so the settings appear to have failed.

The way around this is to configure the SCSI and drive number changes then manually save the CMOS to the USB Fat partition with a *SaveCMOS command. A similar command should be placed in a PostDesk folder, which will need to be created, in !Boot.Choices.Boot so that any CMOS changes are saved to the relevant CMOS file at closedown.

For example :-

SaveCMOS SCSI::4.$.!Boot.Loader.CMOS

There is just one slight snag in that if there is no real time clock the Pi will startup in 1970, until Network time setting completes. On startup the ROM normally reads the time stamp of the only CMOS file it knows about on SDFS and sets its clock initially to that. There is no such CMOS file in a USB only boot if the CMOS slot is empty. It is not a real problem, it just looks a bit odd.

Chris & David,

Thanks for your replies.

@Chris – In answer to your question, I was hoping to leave the SD drive empty and boot 100% from the USB. This would then allow me to use the SD drive as a way to move data between machines.

@David – Thanks for your detailed process. I have carried it out and created the !cmos-save (Obey) file in PostDesk with the SaveCMOS instruction in it.
I also did a manual SaveCMOS as you advised. The manual save did change the CMOS file date/time, but after a restart, there were no more updates.

Even with this change, at startup, It still stops at the Supervisor and with *desktop, takes me to the greyed desktop and that error message “the drive is empty” and !Boot doesn’t run.

Is this because the RISCOS.IMG is still trying to run a CMOS file from the SDFS?

Is it possible to get an edited IMG file that looks at SCSI::4 instead?

I am at a loss as to how to proceed. I guess someone has done it before, but I can’t find a page that explains the best step by step solution.

Any further assistance would be welcomed.

Cheers,

Barry.

stops at the Supervisor and with *desktop, takes me to the greyed desktop and that error message “the drive is empty” and !Boot doesn’t run.

“the drive is empty” means just that, the drive being called is not there, something is adrift in the settings. *status will verify what the CMOS is set to do.

Having got to the desktop the drives should be visible on the icon bar. Clicking Menu on the drive icons will show the filing systems and drive numbers. The intended boot drive should seen.

Is it possible to get an edited IMG file that looks at SCSI::4 instead?

No. The SCSI hard drive is only definitely 4 if there are no other devices.

USB booting is not supported, it requires the user to set it up and cannot easily be supplied as working out of the box. SDFS, on the other, just works.

Edit: I initially couldn’t find these, but there’s also instruction here

It has been a while since I’ve done this using Partition Manager

Here is what I did. Use RISC OS from an SD card to run Partition Manager, then use the Menu Mouse button (scroll wheel) to find the option Initialise Pi Boot Drive, with the pointer hovering over the drive you need to Initialise. Once you’ve set the options you need and it completes, shut down, switch off, remove the SD card and power up.

My setup: an SSD, USB attached via a HUB to a Pi4.

My workflow on reaching the desktop:

Ctrl-F12 to open a task window.

Enter the following based on the knowledge of your system:

co. filesystem SCSI # and press the return key.

co. SCSIFSDrive 4 # The number 4 may differ from your setup.

co. MonitorType EDID

co. AutoDST

savecmos …!Boot.Loader.CMOS # The full path to the CMOS location is required.

Reboot- shut down and restart the computer.

Good luck.

PS there’s a one-time programmable memory on the Rpi that sets where to look for the BOOT

David,

Excellent progress.
*status showed that the CMOS had not stored changes.
*configure filesystem SCSI
*configure SCSIFSdrive 4
*SaveCMOS SCSI::4.$.!Boot.Loader.CMOS

Restarted and it booted without the keyboard error and to the correct desktop.

However, I only see one disk on the Iconbar, and that is the “PiBoot” FAT partition, as created by the RPi Imager and which contains the CMOS, Firmware and Config files.
I don’t have an option to view the ADFS partition with all the apps on, but I can Configure the system using the Menu button on the bottom Right logo, so !Boot is now running.

Application icons on the desktop also run.

Do you know of a way in which I can access both FAT & ADFS partitions?

Would I be better to just use FAT for the whole drive or is that an issue for RISC OS applications?

Sorry if these are silly questions. Still learning.

Thanks for all your help.

Barry.

Do you know of a way in which I can access both FAT & ADFS partitions?

The FAT partition is with a Select-Click (left mouse button) and ADFS is Adjust-Click (right mouse button).

There is *FatSwopMouseButtons to set which icons you want this behaviour swapped for.

Some good help for USB boot is under section 4.2 at: https://www.riscosopen.org/wiki/documentation/show/Raspberry%20Pi%20questions%20and%20answers#TOC4

Do you know of a way in which I can access both FAT & ADFS partitions?

RMKill Fat32FS should sort that. Then remove Fat32 from Boot.Choices.PreDesk. Tested just now with a freshly minted ROOL Pi Image.

The FAT partition is with a Select-Click (left mouse button) and ADFS is Adjust-Click (right mouse button).

That did not work here. Is there a Configure option required for Fat32FS?

That did not work here

Oh sorry, forgot about one thing. If you left-click and it opens the FAT partition, then both left and right clicks will open the FAT partition. You can reset it by going to the menu on the drive and selecting dismount. Now the right click should open the ADFS filer window.

Now the right click should open the ADFS filer window.

It does but only once. After a Select click it reverts to only opening the Fat partition with either click. Checked with Fat32FS 1.64

Without Fat32FS both Select and Adjust open the SCSI partition, the Fat partition is visible as the Loader directory in !Boot.

Thanks to you all for your assistance.

I have kept Fat32FS running as I have a 1Tb FAT32 external drive which I am using for data storage.

I am getting used to using the right key to open the SCSIFS partition, but dismount has become my friend!!

RPi 4 now boots from SSD alone and the CMOS is being saved and loaded from the SSD, so that is all good. :)

Thanks again for your help. Much appreciated.

Cheers,

Barry.

@Rick,

http://heyrick.ddns.net/files/SDCMOS.ffa
Save as “SDCMOS”, settype &FFA (Module).

I have tried downloading this file to see if I can apply this change to my USB drive, but it appears the file is no longer available from this location.

Does anyone know of a different location, or have a copy of this file I can use?

Cheers,

Barry Smith.

appears the file is no longer available from this location

I had a bit of a problem with my new fibre connection recently, so the server was turned off because of that and thunderstorms, haven’t yet gotten around to (read: remembered) to turn it back on.

You can do it yourself. Just load a softload version of the module (not the ROM one) into an editor and change “SDFS” to “SCSI”. That’s all I did.

@Rick,

Thanks for the info.

I will take a look at it when I am back in front of my RPi.

Cheers,

Barry.