Yes, I realise the question is old, but is also one of the first Google results when searching dual boot on this machine.
As the iSSD is used as a cache by Windows, you don't want to install Ubuntu there unless you disable the Windows cache.
As the comment on your question says, the hdd is not cached like that of the Seagate XT drives, but is two distinct drives: ssd on the motherboard, and hdd. Windows is set up to use the SSD as a cache.
You have a couple of options:
- Install Ubuntu on the hdd alongside the Windows install by creating a new partition and installing to that. Ubuntu should be able to use the SSD as a cache, but not sure.
- Turn off the caching in Windows and put ubuntu on the ssd using the method shown by Daniel.
Either way, you'll want a swap on the HDD (on the SSD will kill longevity) as well as a dedicated Linux data partition - Ubuntu can read/write ntfs, but is generally not a good idea to take that for granted.
Here's some partitioning advice - when creating partitions, Linux will need at least / and swap ( or you can use a swap file). It's generally considered a good idea to also have a separate data, or /home. This is for a couple of reasons: if you need to reinstall the OS ( and this goes (especially?!) for Windows as well), you don't then have to go backing everything up and transferring hundreds of GB of data, and; if you fill the data partition then it won't mean a lack of space for Linux to do its required operations in /, in which case it might fall over in a heap. Some Linux admins will advocate having separate /boot, /usr and /var as well, and it is still not a bad idea in the server space where uptime is king, but it's less essential on the desktop.
If it's your first foray into Linux, I'd suggest keeping the /home partition small to begin, and at the end of the drive so it's easier to resize later if you want more room.