Windows 8.1 x86 sees 2.5 GB of RAM from 4 GB, how to fix it?

Question

System administration

Before that, I had 2 GB of RAM, after replacing the strips, a jamb was found by updating the current value in Windows, and:
- BIOS sees all 4 GB
- Debian 8 x86 sees all 4 GB
- Windows 8.1 x86 sees 2.5 GB
I suspect that the problem may be somehow connected with the fact that my Windows is loaded not directly from the BIOS, but through the GRUB multiloader.
I looked at the flags that GRUB passes to Windows, but nothing like the size of the video memory is passed there. I also looked in msconfig -> Boot tab -> Additional papameters - the memory limit is not fixed there either.
How would I fix this without creating a bootable flash drive or reinstalling the system?
PS Processor - Intel Core 2 Duo E6400 (no built-in video adapter).
---
Added another 2 GB of memory using the old slats. Now 6 GB is visible in the BIOS, I ran memory tests - everything is ok. I open Windows, go to the properties of "My Computer", now it says:

4 GB (2.5 GB available)

Previously, with 4 GB on board, it was simple:

2.5 GB

And with 2, if I remember correctly:

1.9 GB

Hmm...

Answer 1

Here is an interesting article

Answer 2

Windows x86 itself does not physically work with RAM greater than 3.4 GB (does not display properly), I suspect that you have an integrated graphics card from Intel that takes on 1.5 GB of RAM.

Answer 3

in the case of Linux or the server version of 32-bit Windows, all the memory would be visible (although applications would still not use it completely, but in this case this is not the point)
There is only one correct solution for you - the 64-bit version

Answer 4

Try swapping the planks.
It often happens to me after cleaning the computer (all the RAM is not displayed). It helped to pull the percent out of the socket, clean it, insert it back.