Knoppix 7.0.5 DVD provides a debug mode if you boot up your system using
Code:
---------
debug64
---------
instead of
Code:
---------
knoppix64
---------
Every time you get a prompt you have to issue 'exit' or press CTRL-D in order to continue. Maybe this will give you an answer what could be done instead of disabling the local APIC.
I booted with the code 'debug64', & it ends in about 2 seconds - with the last output being:

... (other outputs omitted - but it ends with the following)
[ 0.584933] rtc_cmos 00:03 setting system clock to 2013-01-22 21:34:23 UTC (1358890463)
[ 0.586529] ALSA DEVICE LIST:
[ 0.586601] No SoundCards Found.
_ <---- (the dreaded idiot blinky thingy )

It just stays there blinking away until the cows come home.

I rebooted, & tried 'debug' instead, & it's the same output, except it had an extra output line before the mad blinker carret:

... (other outputs omitted - but it ends with the following)
[ 0.954933] rtc_cmos 00:03 setting system clock to 2013-01-22 21:34:23 UTC (1358890463)
[ 0.956529] ALSA DEVICE LIST:
[ 0.956601] No SoundCards Found.
[ 0.958068] input: at Translated set 2 keyboard as /devices/platform/i8042/serio0/input/input2
_

Then I tried both 'knoppix64', 'knoppix', & also leaving it blank at the boot prompt which all resulted in:

early console in Decompress_kernel

Decompressing Linux... Parsing Elf... done.
Booting the kernel

It seems that after 'Booting the kernel' was printed, the system goes to lunch, & never returns.

Then I pop in the Knoppix v6.0.1 CD, & it just blows by everything... detecting 4 cores, & 2 video cards. The processor activity thingy almost never goes any higher than the bottom edge of it's little black box... no matter what I do. But in 7.0.5 with the 'knoppix64 nolapic' entry at boot prompt... extracting, or running any command - like dd - will instantly red line the CPU. Youtube in fullscreen is a big no no.

Do you use the latest BIOS for your mainboard?
The board is up to date... It has been flashed with the latest BIOS bin file.

I wonder what line in the kernel source is triggering the stupidity, & what the same set of lines are in the 6.0.1 source that makes it work. Would be interesting to see what the big difference is.