The braindamaged MBR implementation on PC is regularly circumvented by creating a system partition that fits below cylinder 1024 and in many cases less than 1 GB. This allows the basic OS components to boot and then take over from the BIOS. After this partitions that are 8 ZB big is possbile (
UFS2 2^73).
I suspect GVP implemented something "clever" that obviously isn't compatible..
