Is it (above that = SDXC, rather than SD) a real thing ?
I suppose it may be a BIOS thing, or whatever small devices have instead – or is it to do with FAT ?

googling mostly comes up with opinions on discussion forums, and there’s only one of those that I’d trust 😉

http://www.techrepublic.com/blog/windows-and-office/format-fat32-drives-beyond-32gb-limit/

oooh, and that would make a FAT disc above 32 that ought to work in “anything” that thinks it’s limited to 32 ?

In this instance I think it’s a firmware issue, a device which is designed to take an SD card is not going to go higher than 32Gb, in fact I think a basic SD card would max out at 8Gb, a device with an SDHC capability would go up to 32Gb, and SDXC goes to 128Gb and beyond; I believe a maximimum of 2Tb is mooted for SDXC cards.

What CZ said, in some cases flashing a custom rom can unlock larger capacity if the manufacturer has been lazy and not updated the firmware for the model.

Yup, CZ has it I’m sure.