So I had the same issue where upon reboot, my display would occupy ± 1/4 of the screen and where my icons were messed-up.
Googled something like
ipad icons messed-up upon reboot, found this thread, could not recognize any app mentionned running on my pad.
Was happy though to find a temporary fix adding
com.saurik.mobilesubstrate.dat into the preference folder with iFile.
Nevertheless, was still frustrated because if I would forgot to create the file before reboot, icons would be messed-up again; and that's why I had screenshots of all my screens in my photo album...
Also, after every single respring
or reboot, mobile substrate would crash and I would need to respring again... What a pain...
So, today, I decided that'd be the end of it, and that's why I just registered here, to give you my permanent solution, because you guys deserve to know how I finally got permanently rid of it. First off, thanks to fstbusa for the saurik-dat file, and to Mickey for the common sense.
If the iPad reboots thinking it's an iPhone, indeed, something's wrong, most likely, a tweak's incompatibility.
I discovered that adding the com.saurik file WAS the reason why the springboard would crash, but WAS the solution for my iPad rebooting correctly...
Would have make sense to create the file just before rebooting, not right after, but still a pain; right?
I endured this situation for weeks because I was too lazy to troubleshoot (rings a bell?)
Like I said, I decided that today would be the last day I'd be plagued, so here's what I did...
I went to SBSettings → Mobile Substrate Addons and then,
ONE by ONE, I disabled AND
rebooted, and so on until I fixed the damn thing.
Then I RE-ENABLE IT and only then, I deleted it. ONE by ONE.
In my case, Bigify, Attacher Pro and Unlimited Tones were faulty.
Once I discovered them, got rid of 'em, got rid of the problem.
Hope this helps.