Two modules, 8 GB each...
But the system can only use 8 GB...
I think I saw something like this on some server board with memory mirroring enabled.
If not mirroring, then perhaps the board simply doesn't support more than 8 GB?

8GB seems like a low cap for a DDR4 motherboard, unless it's some lame crap like a notebook with atom or AMD e-series or other low power chip that's deliberately crippled. What's the CPU and chipset?

According to Speccy, the motherboard is:

Motherboard

Manufacturer Gigabyte Technology Co. Ltd.
Model B550M DS3H (AM4)
Version x.x
Chipset Vendor AMD
Chipset Model Ryzen SOC
Chipset Revision 00
Southbridge Vendor AMD
Southbridge Model Carrizo FCH
Southbridge Revision 51
System Temperature 21 °C

BIOS
Brand American Megatrends International LLC.
Version F13
Date 08/07/2021

Voltage
CPU CORE 0.768 V
MEMORY CONTROLLER 2.028 V
VIN2 2.076 V
VIN3 2.028 V
VIN4 0.996 V
VIN5 0.900 V
VIN6 1.224 V
VIN7 1.656 V
PCI Data

Slot PCI-E x16
Slot Type PCI-E x16
Slot Usage In Use
Data lanes x16
Slot Designation J10
Characteristics 3.3V, PME
Slot Number 0

Slot PCI-E x1
Slot Type PCI-E x1
Slot Usage Available
Data lanes x1
Slot Designation J3700 M.2 Slot
Characteristics 3.3V, PME
Slot Number 1

Slot PCI-E
Slot Type PCI-E
Slot Usage Available
Data lanes x4
Slot Designation J3708 PCIE x4 slot from Promontory
Characteristics 3.3V, PME
Slot Number 2

Only Speccy seems to see 16 GB of RAM in the PC - both Windows and the PC's BIOS say that there is only 8 GB. I've enclosed (Bad, sorry, my phone is old) screenshots of the BIOS and the Windows 10 About screen. The next post contains some of the screenshots.

I also enclose the full Speccy report, in speccy, xml, and txt formats.

From: the BIOS

Here are the Speccy reports:

Please,
Do us and yourself a favor and take out the ram, take a photo of the label and post that.
Or if you can take a photo of the label that's on the ram without taking it out, do that.

Kerr Avon wrote on 2022-10-15, 01:51:

Apologies if this is in the wrong forum (and if so, mods, please move it), but how much RAM does this PC have? The screenshot is from the hardware information program Speccy) .

I ask because the physical RAM is reported as being 8 GB, but above that "the memory size" is described as being 16 GB (16384 MB).

Are you using integrated graphics ?

If so, do you have it configured to use 8 GB of video RAM ?

EDIT: Option should be under UMA mode in BIOS/UEFI

Other thing that could be going on is that you have them both in the same channel and one channel only does 2 banks, and there's 4 banks.

Kerr Avon wrote on 2022-10-15, 01:51:

Apologies if this is in the wrong forum (and if so, mods, please move it), but how much RAM does this PC have? The screenshot is from the hardware information program Speccy) .

I ask because the physical RAM is reported as being 8 GB, but above that "the memory size" is described as being 16 GB (16384 MB).

You have 2 ram sticks of 8GB, totalling to 16GB

Kerr Avon wrote on 2022-10-15, 14:38:

From: the BIOS

According to BIOS info your system has 8Gb of RAM. Have you tried to run CPU-Z utility ?

Kerr Avon wrote on 2022-10-15, 01:51:

Apologies if this is in the wrong forum (and if so, mods, please move it), but how much RAM does this PC have? The screenshot is from the hardware information program Speccy) .

I ask because the physical RAM is reported as being 8 GB, but above that "the memory size" is described as being 16 GB (16384 MB).

Your BIOS only reports 8GB, which is also what windows sees.
Whatever speccy reports for your ram is wrong.

RAM
16.0GB Dual-Channel DDR4 @ 1332MHz (20-19-19-43)

Check it physically, open your computer case, or if it has a glass window look through it and see how man dimm modules are inserted on the mainboard.

weedeewee wrote on 2022-10-15, 18:44:

Your BIOS only reports 8GB, which is also what windows sees. Whatever speccy reports for your ram is wrong. […]
Show full quote

Kerr Avon wrote on 2022-10-15, 01:51:

Apologies if this is in the wrong forum (and if so, mods, please move it), but how much RAM does this PC have? The screenshot is from the hardware information program Speccy) .

I ask because the physical RAM is reported as being 8 GB, but above that "the memory size" is described as being 16 GB (16384 MB).

Your BIOS only reports 8GB, which is also what windows sees.
Whatever speccy reports for your ram is wrong.

RAM
16.0GB Dual-Channel DDR4 @ 1332MHz (20-19-19-43)

Check it physically, open your computer case, or if it has a glass window look through it and see how man dimm modules are inserted on the mainboard.

Speccy is not necessarily wrong . If 8GB is statically allocated to the onboard GPU, I am pretty sure that one would see similar results to those shared. I think it's worth checking that before popping the hood, IMHO .

darry wrote on 2022-10-15, 21:09:

weedeewee wrote on 2022-10-15, 18:44:

Your BIOS only reports 8GB, which is also what windows sees. Whatever speccy reports for your ram is wrong. […]
Show full quote

Kerr Avon wrote on 2022-10-15, 01:51:

Apologies if this is in the wrong forum (and if so, mods, please move it), but how much RAM does this PC have? The screenshot is from the hardware information program Speccy) .

I ask because the physical RAM is reported as being 8 GB, but above that "the memory size" is described as being 16 GB (16384 MB).

Your BIOS only reports 8GB, which is also what windows sees.
Whatever speccy reports for your ram is wrong.

RAM
16.0GB Dual-Channel DDR4 @ 1332MHz (20-19-19-43)

Check it physically, open your computer case, or if it has a glass window look through it and see how man dimm modules are inserted on the mainboard.

Speccy is not necessarily wrong . If 8GB is statically allocated to the onboard GPU, I am pretty sure that one would see similar results to those shared. I think it's worth checking that before popping the hood, IMHO .

How do you explain the posted photos of the bios also indicate only one DIMM present? even if it is allocated to the gpu it should show the second dimm in the bios.

and wrt the 8G allocated to the CPU GPU, shouldn't speccy show a second GPU, which it doesn't. Only shows the nvidia 1660 with 2G

Let OP pop the hood and check the hardware.

weedeewee wrote on 2022-10-15, 21:27:

How do you explain the posted photos of the bios also indicate only one DIMM present? even if it is allocated to the gpu it shou […]
Show full quote

darry wrote on 2022-10-15, 21:09:

weedeewee wrote on 2022-10-15, 18:44:

Your BIOS only reports 8GB, which is also what windows sees.
Whatever speccy reports for your ram is wrong.

Check it physically, open your computer case, or if it has a glass window look through it and see how man dimm modules are inserted on the mainboard.

Speccy is not necessarily wrong . If 8GB is statically allocated to the onboard GPU, I am pretty sure that one would see similar results to those shared. I think it's worth checking that before popping the hood, IMHO .

How do you explain the posted photos of the bios also indicate only one DIMM present? even if it is allocated to the gpu it should show the second dimm in the bios.

and wrt the 8G allocated to the CPU GPU, shouldn't speccy show a second GPU, which it doesn't. Only shows the nvidia 1660 with 2G

Let OP pop the hood and check the hardware.

Both good points.

I somehow missed the fact that BIOS shows only one DIMM detected. That said, the manufacturing date in Speccy matches for one of the DIMMs matches the one in seen in BIOS, but the serial number is odd in BIOS. The other DIMM in Speccy looks like it has plausible info .

I also should have looked at the full attached report before posting .

Looking inside the case is definitely a good idea at this point, I concur .

Maybe just needs application of the magic thumb *wiggle, scrunch*

darry wrote on 2022-10-15, 21:09:

Speccy is not necessarily wrong . If 8GB is statically allocated to the onboard GPU, I am pretty sure that one would see similar results to those shared. I think it's worth checking that before popping the hood, IMHO .

Given Bitwrangler's suggestion, I'm assuming speccy might not be wrong and reads the dimm info while the bios does not.

BitWrangler wrote on 2022-10-15, 22:37:

Maybe just needs application of the magic thumb *wiggle, scrunch*

I guess you're right, though still find it odd that speccy reads the dimm info yet the bios doesn't.

Thanks for the answers, everyone. The reason I didn't immediately open the PC up to see how much RAM was physically present was because the PC (which is at a mate's house) was not easily accessible, being behind a desk and tons of of other stuff. But he dug it out last night, and I picked it up on the way to work,, and it did contain two RAM sticks, and four slots. I took the two sticks out, and swapped them around, booted the PC, and now both the BIOS and Windows 10 sees 16 GB of RAM.

I've left MEMTEST86+ running on it, and it's been about three hours now, with no memory problems reported, so hopefully it's all OK now.

I must admit, I am baffled by the cause of the problem, though. Both RAM sticks were in firmly and properly in their slots when only 8GB was being seen by the BIOS and Windows, and they were the correct slots, as proven by the fact that all I did to 'fix' the problem was take out the two RAM sticks and put each one in the other's former socket. I didn't alter any BIOS settings or anything.*

I wouldn't have thought that software (i.e. Speccy) would have been able to see hardware that the BIOS was supposed to see but couldn't.

Anyway, thanks again for all of the help, VOGONs is a great comunity.

* I did enable the BIOS setting concerning Legacy USB support to get the USB keyboard to work with Memtest86+, but that was AFTER I had removed and replaced the RAM sticks and found that both the BIOS and Windows now saw 16 GB of RAM, so that's not relevant to the problem.

BitWrangler wrote on 2022-10-15, 22:37:

Maybe just needs application of the magic thumb *wiggle, scrunch*

Looks like you were right.

My guess as to what happened :

a) Bad connection for one DIMM still allowed for SPD to be readable, which Speccy did

b) BIOS detection logic is more involved than what Speccy does, so BIOS did not get far enough in its detection process to reach attempting to read SPD .

@Kerr Avon Thanks for tge update and glad it works. Say hi to Roj. 😉

darry wrote on 2022-10-16, 15:02:

Looks like you were right. […]
Show full quote

BitWrangler wrote on 2022-10-15, 22:37:

Maybe just needs application of the magic thumb *wiggle, scrunch*

Looks like you were right.

My guess as to what happened :

a) Bad connection for one DIMM still allowed for SPD to be readable, which Speccy did

b) BIOS detection logic is more involved than what Speccy does, so BIOS did not get far enough in its detection process to reach attempting to read SPD .

Oh right. That does seem to make sense, thanks.

@Kerr Avon Thanks for tge update and glad it works. Say hi to Roj. 😉

Well spotted! Blake's 7 is my favourite science fiction program ever, though sadly most modern fans of science fiction have probably never even heard of it.