Having and using two volumes on an iPod 6th Gen classic

[iPodVT]

In order to experiment with exceeding the 128GB LBA28 addressing limitation of a 6th Gen "Original" iPod classic, I flash modded it with a 256GB Samsung Pro Ultimate microSD in an iFlash adapter.  Then I restored/reformatted the iPod with iTunes on a Windows 10 laptop.  As expected, this resulted in a 127GB FAT32 partition/volume and left the rest of the 256GB of storage unformatted.  Then I installed the current dev build of Rockbox, booted into Rockbox Bootloader USB Mode, and used AOMEI Partition Assistant to add another FAT32 partition/volume that filled all of the formerly unformatted portion of the storage.

After all that, when I rebooted into the Apple side, the iPod displayed "Use iTunes to Restore" but I ignored that and connected it to my MacBook Pro (which is where my music library resides).  That caused the iPod to go into Disk Mode and I was able to fully access the first volume for USB file transfers to and from my Mac.  The second volume was nowhere to be found.  But when I again rebooted, this time into Rockbox Bootloader USB Mode, I was able to access both volumes for file transfers to and from my Mac.  The same proved to be true when I rebooted into the regular Rockbox firmware and used its USB mode.

Then I copied my various config/data/etc files onto the first volume, and also copied in all of my music which I divided between the two volumes.  Lastly, I selected the directories for Rockbox to scan and had it build its database.  Everything went well and the database now seems to be happily operating with a music library that is spread across the iPod's two volumes, and I now have a 256GB 6th Gen Classic.  This is fantastic!  There doesn't seem to be any corruption occurring from booting into the Apple side despite the fact that "Use iTunes to Restore" gets displayed.  The only 'loss' is that I can no longer use the iPod as a DAP when booted into the Apple side, but I don't care very much about that because I already have been using Rockbox pretty much 100% of the time.

Windows 10 doesn't seem to allow me to access the iPod at all in Apple Disk Mode - it seems to require Rockbox Bootloader USB Mode - I don't remember whether or not it allowed access via Rockbox Firmware USB Mode.

At some point I hope to figure out how to get the necessary software libraries installed onto one of my computers in order to get mks5lboot to work for me so that I can prevent the iPod from booting into the Apple side at all, and then I would be able to have a 256GB 6th Gen classic with a single volume that won't get corrupted by the Apple firmware.  But for now I'm more than happy.  And in my 6th Gen's present setup I can still access the iPod's Apple Diagnostic Mode.

A few stats:
I use an old Windows 10 laptop for reformatting/restoring iPods with iTunes, and I use a 2012 MacBook Pro running macOS 10.13.6 High Sierra with iTunes 12.8.3.1 and the FreeFileSync app for managing the iPods.  With this particular newly modded 6th Gen Classic, I'm generally seeing file transfer speeds between 13.5 and 14.4 MB/Sec regardless of which mode I'm in;  Rockbox Bootloader USB Mode seems to be a little bit faster than both Apple Disk Mode and Rockbox firmware USB Mode.

[Frankenpod]

So you have two separate partitions, rather than one >128GB partition/"disk"?

What happens if you use Rock Box's file browser, rather than the database?  Can it "see" the second partition?  How does it show the contents?  Would seem a little odd if the database can access the second partition but the file browser can't.

[iPodVT]

As far as I can tell from what I have observed so far, everything seems to be as fully functional as if the iPod had only one volume.  The file browser has <HDD1> as its first entry at the top of the list - that is the second volume.  The first volume is specified by <HDD0>, though that does not appear in the File Browser.  If you click on <HDD1> the browser enters the second volume.

I've attached three photos:  the first shows the top level of the file browser, the 2nd shows the top level inside <HDD1>, and the third shows the Rockbox Info screen (accessed via System->Rockbox Info).  Notice that the two volumes are listed at the bottom of the Rockbox Info screen, and each one's capacity and available space are specified.  The first volume, <HDD0>, is listed in the "Full Path" entry in the Rockbox Info screen.

[iPodVT]

Only the third photo was uploaded so I am trying again, here, to upload the first two photos.

[iPodVT]

Well, in my second attempt only the second photo was uploaded, so here is the first one (I hope)...

[iPodVT]

Okay, all three photos are uploaded, albeit in reverse order.  Sorry about that.

[iPodVT]

So you have two separate partitions, rather than one >128GB partition/"disk"?

[Edit]
Yes - that is correct.  From what I have read of other users' experiences, if I had expanded the first partition, corruption would occur if I were to boot into the Apple firmware.  It seems that if the size of the first "legit" partition is not expanded from its 'legal' allocation (and maybe also not shrunk), corruption will not occur when you boot into the Apple firmware.  I'm guessing that the Apple firmware is satisfied if the first partition remains as expected, and the firmware doesn't look at or care about what might be beyond that first partition.

My curiosity makes me want to try shrinking that first partition to see what would happen.  But not at this time.  For now I am more than content...

[Frankenpod]

Interesting.  Very Useful to know that it works like that.  Curious why RB itself seems to treat the second partition as if it were a folder within the first one.  Can a developer say if that's the intended behaviour or if it sort of works by accident?

Going back to an old thread where I was wondering about this issue, I never got round to trying rockbox_dev123's suggestion (for preventing it booting in OF) - maybe it would work for you here?  Just entirely self-interestedly suggesting it because I'd be interested to know if it works.

https://forums.rockbox.org/index.php/topic,54703.msg252999.html#msg252999

I've given some context that is hopefully useful in the previous messages I quoted.

Another thing that you can do - without needing to reflash the bootloader - is just to delete or erase the partition that holds the OFW. This should be a simple way to prevent it from booting.

[iPodVT]

Going back to an old thread where I was wondering about this issue, I never got round to trying rockbox_dev123's suggestion (for preventing it booting in OF) - maybe it would work for you here?  Just entirely self-interestedly suggesting it because I'd be interested to know if it works.

https://forums.rockbox.org/index.php/topic,54703.msg252999.html#msg252999

I've given some context that is hopefully useful in the previous messages I quoted.

Another thing that you can do - without needing to reflash the bootloader - is just to delete or erase the partition that holds the OFW. This should be a simple way to prevent it from booting.

Haha - not only do I now remember having previously seen that thread - I was also a contributor to it.

Isn't that effectively the same as what is demonstrated in the video on the iFlash website [https://www.iflash.xyz/how-to-rockbox-installation-on-ipod-classic-using-new-bootloader/]?  I think I tried it once and when the bootloader tried to boot into the OF, corruption occured even though the OF wasn't there.  I might be misremembering...

In any case, the more I think about it the more I like the fact that Apple Disk Mode and Diagnostic Mode are both still available to me with my current setup.

I'm also now wondering if I were to delete the second partition would the OF once again be fully functional as when the iPod was initially reformatted/restored?  I bet it would.  So, another thing to try.  But I can't (or shouldn't and am trying to not let myself) spend any more time on it this week.

[iPodVT]

Interesting.  Very Useful to know that it works like that.  Curious why RB itself seems to treat the second partition as if it were a folder within the first one.  Can a developer say if that's the intended behaviour or if it sort of works by accident?

I'm guessing that they just display it that way because it was probably a lot easier and faster to implement than having to redesign the file browser UI for a truer visual representation of the hierarchy of two sibling volumes above each one's descendent directories and files.  The functional user access is basically the same either way.

[iPodVT]

I'm guessing that they just display it that way because it was probably a lot easier and faster to implement than having to redesign the file browser UI for a truer visual representation of the hierarchy of two sibling volumes above each one's descendent directories and files.  The functional user access is basically the same either way.

Thinking about it a bit more, it occurs to me that the first volume is the dominant volume where the RB firmware has to be, so the second volume is like an auxilliary appendage - not an equal sibling - and it makes conceptual sense that the second volume is accessed through the first volume.  But these thoughts are just my musings and projectings - the real and definitive explanation can only come from the developers who implement this truly great stuff for us.

[Frankenpod]

Hmmm, thanks for doing that - I started experimenting with a 6th gen (hence the previous thread) but in the end couldn't be bothered and just got more 7.5gen logic boards (and cannibalised the 6th gen parts for those).  Very useful to know that separate partitions works much better than one big one.

So the residue 'glitch' is that when booted into OF it doesn't function but shows the 'use iTunes to restore' message?  I wonder why it does that?  Seems to imply that while the OF can't use the second partition, it's somehow aware that it's there and objects to that situation.  If there were any way of getting round that (i.e. making it so the OF only sees the first partition and functions as if it were the entire disk) it would be a complete solution/work-around.

[iPodVT]

Once again, I'm just musing (and should probably stop doing so...):

I'm guessing that the OF trips as soon as it sees that the MBR indicates a main partition greater than 128GB and/or the presence of any additional partitions beyond the 128GB limit.

Another interesting experiment - for knowledge sake only - would be to try formatting the 6th Gen with just one undersized partition and see how the OF reacts [edit: I'm guess the OF would be fine with that - it would be the same as installing an SD that is smaller than 128GB] .  If the OF is cool with that, then try formatting with two partitions that together stay within the LBA28 limit and see what the OF makes of that.  Again, just for knowledge sake, and as David Byrne sang, "I ain't got time for that now..." (though I increasingly desperately want to do the experiments).

[rockbox_dev123]

I'll join in for some musing.

Following the iPodWiki firmware page here: https://ipodwiki.com/wiki/Firmware

It shows that the iPod classic (6th generation) can take firmware up to 1.1.2.

However the iPod classic (7th generation) can take firmware up to version 2.0.5.

(Rockbox does not make a distinction between 6th and 7th generation and considers them all 6g.)

I've always wondered where the 127G limit comes from on the 6th generation classic. AFAIK the hardware is almost identical between 6th and 7th. I would imagine that it is a firmware limitation (which lives on disk?).

Has anyone restored an iPod 7th with a capacity of more than 127G and then connected that drive to a 6th gen to see if it can run higher firmware versions than iTunes will allow it to?

[iPodVT]

Has anyone restored an iPod 7th with a capacity of more than 127G and then connected that drive to a 6th gen to see if it can run higher firmware versions than iTunes will allow it to?

If it doesn't work in a 6th Gen, perhaps it might in a 120GB 6.5 Gen as those can take OF up to 2.0.1.