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.
HP ProLiant ML350 Gen 9 Server 64GB RAM 2.4GHz Xeon 12-Core E5-2667 v3
$300.00
1U Supermicro Server 10 Bay 2x Intel Xeon 3.3Ghz 8C 128GB RAM 480GB SSD 2x 10GBE
$273.00
Dell Poweredge R730xd 3.5 2x E5-2690 v3 2.6ghz 64gb H730 14x Trays 2x 1100w
$489.99
Dell Poweredge R630 2x Xeon E5-2680 v4 2.4ghz 28-Cores / 128gb / H330 / 2x 1TB
$279.99
Dell PowerEdge R620 Server - 256GB RAM, 2x8cCPU, 120Gb SSD/3x900Gb SAS, Proxmox
$320.00
R630 DELL 8 x 2.5'' POWEREDGE 2X E5-2680V4 32GB RAM IDRAC ENT & NDC 2X 495W PSU
$172.95
SuperMicro Server 505-2 Intel Atom 2.4GHz 8GB RAM SYS-5018A-FTN4 1U Rackmount
$202.49
CEOhack 1U X9DRW-3TF+ 4 Bay Server 64GB DDR3 1x E5-2667 V2 3.30GHz 8C 1x 1TB HDD
$119.00
Lenovo x3550 M5 1U Server 2x Xeon E5-2680 v4 2.4ghz 28-Cores 128gb M5210 2x750w
$399.99
HP ProLiant DL380 Gen9 16SFF 2x E5-2620v4 2.1GHz =16 Cores 32GB P840 4xRJ45
$267.00