Vanilla Amiga OS 3.1 has a scsi.device (think hardware driver) that can only talk properly to storage devices up to 4GB in size. Disks bigger than that will get corrupted as any sector offset bigger than the 4GB boundary rolls around back to zero.
For a long time there has been patched unofficial scsi.device files and in Amiga OS 3.9, an official scsi.device that doesn't have this limitation.
Hardly any real[1] Amiga fan runs stock Amiga OS 3.1 - most of us have loads of patches in our startup-sequences to overcome modern day issues.
---
[1] There is a large segment of the Amiga community who only game on their Amigas using 4GB CF cards on the IDE channel and a product called WHDLoad (http://whdload.de/), they do not care about the OS so don't fiddle with it.
