I have a Mac Pro and Have successfully loaded 2 separate hard-drives with openSUSE. 1 with a GNOME desktop and 1 with KDE. I have posted a HOW TO on the forums here => How To Install openSUSE 11.2 on Mac Pro in it’s own hard-drive. - openSUSE Forums
The trouble I am having is difficult for me to understand. I can have them internally mounted and they will only default to the one that was used last. If I pull the hard-drive of the one that was used last I must redo the steps to repair the installation of the one that is left before it will mount, otherwise it goes to the screen to mount GRUB but only shows GRUB _ . So when I get this one repaired and it works flawlessly I can shut down my computer and pull the hard-drive and replace it with the other and I get GRUB _ . So with out repairing if I put the other one back in it works flawlessly. So How is it writing a state to memory if the computer has been shut down, that should parse the memory.
Please help me to understand what I am faced with and if there is a special way I can configure GRUB to allow me to do both or not. 
Thanks
So, I do not use a MAC. However, you do not need two different loads of openSUSE to have both gnome and KDE in the same single installation. Lets say you use the KDE load. open up Software Management, Pick the View button on the top left and pick Patterns. Under Graphical Desktops you can check and load GNOME base system and GNOME Desktop environment. This will load the required files for the GNOME system into the same load as KDE. You do not want to set autologin as you select the session type, KDE or GNOME, before you log in.
Now if you installed openSUSE from a Live CD, that only contained KDE or GNOME, you may need to add some installation sources for the GNOME environment. The GNOME repositories are located at:
Which must be added to your Software Repositories. I do not know for sure what your two openSUSE installs are doing, but why not just use one install?
Thank You,
I know it doesn’t sound helpful, but look at the grub how-to’s on one of the linux doc sites or by installing the suse howtos. (try looking at The Linux Documentation Project)
Generally, fixed drives remain fixed and aren’t swapped randomly.
It depends on where you have installed the bootloader - on a patition or in the mbr.
If you are swapping disks, you need an identical grub in each disk’s mbr to allow it to boot.
Logic dictates that if the grub pointer is to a non existent drive or partition, it will not boot the referenced system.
(Grub entries are from a file - /boot/grub/menu.lst or grub.cnf, depending on version - and are a not dynamically written on boot.)
Only one version can be active at one time and that is the always the one that is referenced from the BIOS primary boot hdd.
So the GRUB writes to the BIOS that is interesting, that explains the fact it stuck around even after shut down and hard drive switched.
@jdmcdaniel3 I will try the dual desktop setup you suggested it was also suggested in another post I had. I was experimenting with Linux installs. I will probably want to load another distribution of Linux on the other drive. I was intending to see if they would coexist on the same computer with 2 known working Linux environments before discounting that the other Distribution was not right for me without ever giving it a chance.
@whych I will definitely read up on the grub subject as I am interested in maybe finding a way to alter the grub in a way to launch what I want.
Thank you both. 
No Grub does not write to the BIOS. The BIOS is set up to go to the MBR block on the first bootable device and start the code there. There is also a partition table and some other info in the MBR. The MBR is where grub or any boot controller writes the code that will chain to the menu code. There is nothing special about grub all booting on PC’s work more or less the same.