I don't think it is very fruitful to discuss upper memory for 32-bits processors. In my first reply, I just wanted to point out that the "non-detection" is quite normal, and I would hardly call it an error that Knoppix is configured more restrictively than possible with the latest gen processors. And what really makes this a non-issue, is - I also pointed this out - if one needs to use all RAM, start in 64-bits mode. (To stuff a 32-bits machine with 4+ GB RAM seems rather meaningless to me, but it can of course be done, kind of retrocomputing bringing back memories of 16-bits computing and a total of 20 bits address space. 64G addressing (32+4 bits) on 32-bits is analogous, and to me hardly more attractive when you get a decent 64-bits computer for a few hundred dollars.
I'd like to get back to discussing booting. I personally think grub4dos may be the best way to go, legacy grub is too limited and grub2 has gone astray.
