I've set up a triple boot system (Ubuntu Karmic, Windows Vista and OSX86 -- a patched OS X which works on a PC) on a Dell 9200 (C2D 2.13 GHz, 4GB RAM, nVidia G210).
I sue Grub2 as the bootloader and update-grub picks up OS X and it boots without any problem.
However, although when booting OS X using its own Darwin bootloader, I can apply the boot option "Graphics Mode"="1680x1050x32" to ensure that I get the screen resolution that I want, when OS X boots from Grub2, the only resolution available is 1024x768 which is disappointing.
I have tried adding gfxmode=1650x1050x32 to the OS X section of /boot/grub/grub.cfg in Ubuntu but this does nothing.
Can anybody offer any advice as to how I might include a viable boot option for OS X in Grub2?

try gfxpayload iso gfxmode ... check out this.

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Oh, and I just came through this blog entry, how to pass parameters directly to the kernel.

Hi thecarpy

Thank you very much for those two very useful replies.
Yes, putting the simple line
into the OS X section of /boot/grub/grub.cfg allowed me to boot OSX86 through Grub2 at the desired resolution.
Although I haven't tried it yet, the second reply also shows how to chainload OS X from Grub2 (which is not as simple as chainloading Windows). So, assuming that will work for me, it should mean I can boot OSX86 through Darwin from Grub2.
As Darwin recognizes com.apple.Boot.plist while Grub2 doesn't, and as I've included the kernel flag "Graphics Mode"="1680x1050x32" in the Boot.plist file, this should also allow booting to the desired resolution from Grub2.
Excellent.
Thanks again