Half of my RAM is hardware reserved

Yes...

It have to be the UEFI/BIOS....
You are not using the integrated iGPU I guess, so you could just disable it if it is enabled...in BIOS.
You may even also have to justify the memory....I'm not sure.

My screen looks different than the one in the manual, which is below


Mine doesn't have a line for disabling the integrated graphics. I disabled the IOMMU but that didn't change anything.

- - - Updated - - -

I went ahead and reset the IOMMU to Auto

May there is a registry value too for disabling the integrated graphic...

"I went ahead and reset the IOMMU to Auto"....it may will work.

You may even disable it through Device Manager.
Open ‘Device Manager’ in Windows PC via Windows Search Box and expand ‘Display Adapters’ category.
Right-click on your integrated graphics and select ‘Disable Device’ to disable it. Click ‘Yes’ if asked for confirmation. Once done, check if the issue is resolved.

I found this online from someone with the same issue:
the ASRock B450M Pro 4 auto-detected the ram to be 2666 MHz, when they are actually 2933 MHz. I assume this is what caused Windows to render half the ram unusable. After correcting the speed in the BIOS, problem was solved, all 16GB were available again.

I don't know where to check this on my BIOS

B450 AORUS PRO WIFI Motherboard｜AORUS - GIGABYTE Global
Attachment 384786

Is this your motherboard?

Your CPU doesn't support integrated graphics, and that may be why there is no BIOS setting available - but that leaves the mystery of what has reserved the RAM.

Memory speed: see 'advanced frequency (& memory) settings' on the MIT tab. I have no idea what you will find there, I am just reading the manual.

LuCal said:

I found this online from someone with the same issue:
the ASRock B450M Pro 4 auto-detected the ram to be 2666 MHz, when they are actually 2933 MHz. I assume this is what caused Windows to render half the ram unusable. After correcting the speed in the BIOS, problem was solved, all 16GB were available again.

I don't know where to check this on my BIOS

Attachment 384787
Have a look under Advanced Memory Settings

Someone else had a similar issue and this is the resolution:
UPDATE I fixed one of the problems!!! turns out in my bios my manual timings for my ram were wrong. I corrected them and suddenly all 16 gb are being recognised and only 70mb are hardware dedicated!!!

I don't know how to check or change the manual timings for the ram in the BIOS

LuCal said:

Someone else had a similar issue and this is the resolution:
UPDATE I fixed one of the problems!!! turns out in my bios my manual timings for my ram were wrong. I corrected them and suddenly all 16 gb are being recognised and only 70mb are hardware dedicated!!!

I don't know how to check or change the manual timings for the ram in the BIOS

Look at my last post...is this your motherboard? Please confirm yes or no.