Hello,

I can't use my whole RAM capacity !

I have a 16GB kit (4x8GB) and only 8GB usable in windows 10 and the other 8GB is "Hardware Reserved". 

In bios the 4 DIMMs was detected properly with the correct capacity.

most probable is the ram sticks are not properly inserted into the slots (this has been quite common on ryzen boards)

second place to look is the actual cpu seating, this also has been a problem

worst case is slightly bent pins. usual case (if it is the cpu seating is a remove-refit makes the contact clean)

TRY THE RAM FIRST !

another clue might be the bios says 'single channel' this would point more likely to bad insertation of the ram sticks

Indeed, the bios displays 'single channel' !

Yet I checked and still checked, the RAMs are properly installed. The BIOS detects them very well too.

I searched a little on the web. Apparently, it's related to Memory Remapping but I did't understand everything. There is my configuration :

CPU : AMD Ryzen 5 2600X

GPU: GeForce GTX 1060

RAM : DDR4 HyperX Fury, 4 x 4 Gb

(Sorry for the mistakes, I don't speak English very well)

Thanks you.

ok carefully remove the cpu

visually check for slightly bent pins (or maybe some excess thermal paste on pins)

and then reseat the cpu into socket 

p.s.  if the bios was detecting them properly, it wouldnt be saying 'single channel' it would say double channel

Done, I checked the CPU. The problem doesn't seem to be that :/

I also tested with two of 8 GB. Again, the problem was the same, only 8 usable

ok so now move onto testing the ram and the slots

one at a time

one stick in slot a2 check it reads 4gb

next stick check that

untill all four sticks have been checked in slot a2

if all 4 sticks are ok

next test one stick in slot a1

then b1

then b2

see what happens

so ?

all 4 stick show 4gb when inserted by themselves into slot a2 ?

and all 4 sticks also show 4gb when inserted by themselves into slot a1/b1/b2 ?

so you have proved each stick works properly in each slot on its own ?

if so i would be inclined to presume a fault with either the cpu or the board

have you also reset the bios to defaults ?

Yes.

If I put one stick (so 4GB) I can use 4 GO. There is not RAM reserved. Let's try to reset the bios !

problem with cpu or mainboard then i feel

1 stick should go into slot a2 (says single channel) 4gb

2 sticks should go into a2/b2 (says dual channel) 8gb

4 sticks into a1/a2/b1/b2 (says dual channel) 16gb

well then thats confirmation of the problem

soooooooo if you bought from a shop /retail outlet return the parts /system explain and they can change the faulty part

card or cpu seems to be messed up

its hard to tell ,but im sure its not software