For those of you that have tried installing a 64 bit kernel on a new intel box, the machine wont boot from media if the processor makes use of DMAR graphics engine.
When trying to boot Linux from the media (DVD/CD-ROM), upon loading the system files and standard drivers, the system hangs after the loading kernel screen.
Late quad core processors present this issue becoming a royal pain in the ass:
IOMMU: Setting identity map for device 0000:00:1a.1 [xdefd6000 - 0xdefd7000]
To solve this issue, you have to disable the graphics mapping Intel engine. On the initial GRUB installation screen lets edit the kernel parameters by pressing E; Then we just append the following phrase:
intel_iommu=off
Press B to boot and the system will start normally.
OK, but we don’t want to do this every time we power on the machine. There are two easy ways around this, the former being the recommended choice:
a) After the first successful booting, upgrade to the latest version of the kernel.
b) If you refuse to update your kernel, edit grub.conf to boot without loading DMAR.
Its up to you to decide the best way.
This also works on a Dual core with fedora 9 x64