Getting into Linux, installed Centos 7 on an old workstation that had Vista on it. System has four memory slots where the system had 2 x 1 gig sticks, and 2 x 512 meg sticks, for a total of 3 gigs (DDR 2).

I took three sticks out and put 3 x 2 gig memory sticks, and left one of the original 1 gig sticks. This should equal 7 gigs.

Centos still sees the system as having 3 gigs.

The thing is, I do not know if the motherboard supports more than 3 gigs of memory.

I was playing around with this until bedtime last night and will get back on it when I get home.

When I get home I will get into the bios and see if the motherboard is seeing the 7 gigs of memory.

Until I get home this evening, the question is:

Will Centos 7 see added memory, or do I need to change something on the OS?

This is an older Gateway FX desktop with a core 2 quad cpu. I do not remember who made the motherboard.

Yes. If the computer (the BIOS) knows about it, so does normally Centos. You could check for error or warning messages in the message buffer at early boot time. Use the dmesg command.

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No, at most 6 GB as "pairs" of memory sticks should be identical, so AT MOST it is seen as 2x2G plus 2x1G (if the motherboard accepts those 2 GB sticks).
Also make sure the (better keep both 1 GB sticks in the system) first two slots are filled with the larger sticks, so slot 0 and 1 with 2 GB, 2 and 3 with 1 GB to reach that total of 6 GB
Or, IF the motherboard can handle 2 GB sticks: buy a 4th one for 8 GB total (at least all the sticks then are identical).

Seems you like to go by the book. Yes, that is the way things are "supposed" to go.

In real life I have been mixing memory on computers for close to two decades and rarely if ever have an issue.

Motherboards usually do good at sensing the memory and getting things to work.

And does with an Intel Core 2 cpu, as that is a two-way interleave processor, so needs its memory in matched sizes.

You think using the single one gig stick is preventing the system from seeing the other 4 gigs? Maybe it would be better to take that single stick out with the matching stick on the other slot and see if I can at least get 4 gigs.

I found the system on an old Cnet page, which says the computer supports 8 gigs of memory.

I would at least start the troubleshooting there. Make sure it sees 2x2 first, then see if you can add an additional 2x1.

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Sounds like a good idea.

Will replace the 2 gig module that matches with the 1 gig with a 1 gig, this will be 2 - 1 - 2 - 1 . Hopefully get 6 gigs. Go from there and see what happens.

It was late last night when I put the memory in and did not have a lot of time to play with it.

Got home, ate dinner, switched one of the 2 gig memory modules out with a one gig, 2 - 1- 2- 1, system still shows three gigs of memory.


Rebooting, going to check bios... go from there

Took 2 chips out, left two of the two gig. 2 - empty - 2 - empty. Centos still showed three gigs of memory. Put memory back in with the two 2 gig sticks along with the two 1 gig. Rebooted

Rebooted, system showed the bios screen for a split second, and I was able to hit pause. Motherboard shows 6 gigs of memory. I got my camera and took a picture if yall want to see it.

So what would cause the OS to only see 3 gigs. Its almost as if a 32 bit os was installed.

My kernel version - 3.10.0-1062.1.1.el7.x86_64

~~~~~ EDIT ~~~~~~

Maybe I could reinstall with the new memory? This is a fresh install so nothing would be lost.

~~ EDIT 2 ~~

[root@unknown00E0B8E6C968 ~]# sudo lshw -class memory
*-firmware
description: BIOS
vendor: American Megatrends Inc.
physical id: 0
version: 080014
date: 01/14/2008
size: 64KiB
capacity: 512KiB
capabilities: isa pci pnp apm upgrade shadowing escd cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer int10video acpi usb ls120boot zipboot biosbootspecification
*-cache:0
description: L1 cache
physical id: 5
slot: L1-Cache
size: 128KiB
capacity: 128KiB
capabilities: internal write-back data
configuration: level=1
*-cache:1
description: L2 cache
physical id: 6
slot: L2-Cache
size: 8MiB
capacity: 8MiB
capabilities: internal write-back unified
configuration: level=2
*-memory
description: System Memory
physical id: 25
slot: System board or motherboard
size: 6GiB

But free command shows 3 gigs

[root@unknown00E0B8E6C968 ~]# free
total used free shared buff/cache available
Mem: 3172048 1280780 1025480 89900 865788 1642960
Swap: 3145724 0 3145724

System monitor shows three gigs of memory.

Does that machine have the ability to boot from USB? If so, can you create a CentOS 7 install USB just to see if the live image sees the full available ram? Or ANY live linux really? Just to test that the mobo is passing the information properly to the OS (I have seen this happen with old, early generation 64-bit motherboards).

Thank you and yes, I installed the OS with a bootable thumbdrive.

What do I need to do?

Reboot the system with the thumbdrive, then what? I am not sure what you meant by "live image."

Live image - Any OS that can run from a USB (or cd/dvd but obviously that's a lot slower) and doesn't just go straight into an installer. You're not needing to actually do anything, just boot to a USB environment with whatever OS you can, verify how much ram said environment sees.

This step is strictly to rule out the bios/bootloader communication as the issue.

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Thank you. Last night I did a fresh install of Centos 7. During the install I selected reclaim the drive space. This was to check if Cent was not seeing the memory upgrade.

Same issue with a fresh install, the OS sees only 3 gigs of memory.

This morning I downloaded Ubuntu, created a bootable flashdrive, booted into Ubbuntu, brought up terminal and ran sudo lshw -class memory

memory
description: System Memory
physical id: 25
slot: System board or motherboard
size: 6GiB

The memory display shows the correct size size memory module in the correct slots.


Top command says KiB Mem : 3328596 total.

System monitor - resources - memory - 3.2 gigs.

The motherboard shows to have 6 gigs of memory, but for some reason neither ubuntu or Centos can see no more than 3 gigs.

ubuntu@ubuntu:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.3 LTS
Release: 18.04
Codename: bionic

I don't suppose there's a BIOs update for that board? Sounds like it's a BIOS issue. Some of the early generation Athlon 64 boards I saw the same thing in.