Bios Mods -The Best BIOS Update and Modification Source

Hi,

For the fun I have upgrade my old laptop a Toshiba Tecra S5 with 8gb ram.
Yes, the specifications say: max = 4gb ram.
The BIOS see the full 8gb ram, my OS, Linux Mint 18.2 - 64 bits only 4gb.
Somewhere in the BIOS this is blocked at 4gb.

But is it possible with loading a custom DSDT to have the full 8gb.
If yes, where do I have modified the 'dsdt.dsl' file?
Info: http://blog.michael.kuron-germany.de/201...compiling/

Attachment, TecraS5.zip with additional info.
- 'Screenshot' of my BIOS with the full 8gb = Foto-8192.JPG
- Output of 'sudo dmidecode' = BIOS_TecraS5.txt
- Output of 'sudo fwts' = results.log
- Disassemble of the DSDT (/sys/firmware/acpi/tables/DSDT) = dsdt.dsl

Thanks in advance.

Update...

Playing with my memory modules.

1x 4gb - The BIOS sees 4gb - Linux Mint 18.2 64bits too.
1x 4gb + 1x 2gb - The BIOS sees 6gb - Linux Mint 18.2 64bits too.
2x 4gb - The BIOS sees 8gb - Linux Mint 18.2 64bits only 4gb.

Very odd.