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Originally, I had 4GB of RAM (4*1GB), and everything worked like a charm.
A few months ago one of my memory cards got bad, so I had to take it out and throw it away.

A few days ago I bought 2 new identical cards and installed them,
so there are 2*1GB of one manufacturer (kingston), and 2*1GB of another (CEON).
In total it should bring me back to 4GB dual channel.

CPU-Z reports they are all installed (CPU-Z report),
but when BIOS is starting it shows 3145728K, and windows also recognizes only 3GB (system information).

So... Where's the problem?

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    I thought this was going to be an easy question. 32 bit system. NOT. 1 bad RAM module. NOT.
    – fixer1234
    Oct 8, 2014 at 16:44
  • @fixer1234 - What?
    – Ramhound
    Oct 8, 2014 at 17:06
  • Which ones did you JUST add, the Kingston or the CEON? What motherboard make and model are you using?
    – Ƭᴇcʜιᴇ007
    Oct 8, 2014 at 17:15
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    IF you use just the new RAM, does all 2GB show up as expected?
    – Ƭᴇcʜιᴇ007
    Oct 8, 2014 at 17:39
  • You should test the RAM modules one by one and possibly the slots one by one.
    – pabouk - Ukraine stay strong
    Oct 9, 2014 at 10:40

1 Answer 1

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Due to an architectural decision made long ago, if you have 4GB of physical RAM installed, Windows is only able to report a portion of the physical 4GB of RAM (ranges from ~2.75GB to 3.5GB depending on the devices installed, motherboard's chipset & BIOS).

This behavior is due to "memory mapped IO reservations". Those reservations overlay the physical address space and mask out those physical addresses so that they cannot be used for working memory. This is independent of the OS running on the machine.

Quoted from: http://blogs.msdn.com/b/hiltonl/archive/2007/04/13/the-3gb-not-4gb-ram-problem.aspx

From the CPUZ factsheet, the mobo is i945. Read more: https://forum-en.msi.com/index.php?topic=123711.0

In simple words: Or, a Windows 64-bit computer may show only 7.1 GB of usable system memory when 8 GB of memory may be installed. This is because usable memory is a calculated amount of the total physical memory minus “hardware reserved” memory. http://www.thewindowsclub.com/computer-ram-graphics-card-video-memory

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    If I interpret his screenshot correctly, he has a 64-bit version of Windows installed. Memory is remapped, so it’ll remain accessible.
    – Daniel B
    Oct 11, 2014 at 17:27
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    You made 3 mistakes: It worked with 4GB before, problem shows before OS loads (in POST) and he attached report from 64bit system, while the thing you're linking refers to 32bit Windows.
    – Agent_L
    Oct 11, 2014 at 17:43
  • @Agent_L please read it care fully first.
    – Gaurav Joseph
    Oct 11, 2014 at 18:49
  • @DanielB please read the post i referred to before downvoting.
    – Gaurav Joseph
    Oct 11, 2014 at 18:54
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    We did; What you quoted has NOTHING to do with 64-bit installtion of Windows like the author is using; so your answer is not helpful even in the slightest. I had the same CPU had no problem using 8GB of memory and before that 4GB of memory
    – Ramhound
    Oct 11, 2014 at 19:05

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