[OpenIndiana-discuss] How to boot oi-dev-151a7-ai-x86.usb inot 64-Bit mode ?

[x11max Unitymedia]

Hi, 

my problem is, that it is not possible to boot oi-dev-151a7-ai-x86.usb into 64-bit mode on the system I would like running openindiana on.
It comes up in 32-bit mode only.

On the download site there is a hint:  

All downloads support both 32-bit and 64-bit processors. 64-bit mode is automatically selected if at least 900 megabytes of memory (RAM) are available.

I have 16G RAM installed, so more than 900 megabytes of memory are availale, but openindiana always boot in 32-bit mode. 
Because I have two 2TB disks installed, it is not possible to run the installer. 

My system information: 

Asrock Z68 Pro3-M Sockel 1155 Mainboard (Micro ATX, Intel Z68, 4x DDR3 Speicher, 2x USB 3.0)
Intel Core i7-2700K Quad-Core Prozessor Boxed 3,5GHz, Sockel 1155, 8MB Cache
16GB RAM
2TB Disks

My question now is how to run the usb installer in 64-bit mode ? 
How to change the GRUB startup manually to point to 64-bit kernel ?
Or it is possible to make oi-dev-151a7-live-x86.iso bootable on an usb device ?

The ISO file oi-dev-151a7-live-x86.iso contains a directory /platform/ipc86/kernel/amd64/. 
So i can change the grub startup to load the 64-bit kernel if installing openindiana in a virtual machine.

On oi-dev-151a7-ai-x86.usb there are only 32-bit kernel available and I can't choose the 64-bit kernel for startup.