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Installing more RAM than stated maximum

  1. #1
    A College Professor Naturally Camouflaged [your moreover breastless limestone]
    I did this successfully on a Lenovo x230, everything published says it can have 8GB max but I put 16gigs in it from my broken lappy and it booted up and shows 16gig in dxdiag.

    When I look this question up it's a bunch of nerds saying either the machine won't work or only the stated memory capacity will be usable.

    Are they talking out their ass? My desktop motherboard states 16gb max which is what's installed and I would like to install more, is it likely to be able to utilize 32 or 64gigs? Coz it takes ddr3 and there are 32gig sticks available and it's got two slots
  2. #2
    aldra JIDF Controlled Opposition
    it may not recognise the extra RAM, but as long as it detects properly in BIOS/UEFI it'll work fine
  3. #3
    -SpectraL coward [the spuriously bluish-lilac bushman]
    On every motherboard, there is a controller for accessing the RAM. The limiting factor is how much memory can be accessed (or addressed) by that memory controller. Theoretically, a 64-bit CPU can access 2^64 bytes of RAM. For practical reasons, however, the number of addresses lines actually etched into a motherboard is much smaller, and the controller is created to be able to access up to a specific number of addresses. It can address fewer memory locations just fine as well. That determines the range and maximum amount of memory.

    So when memory is installed with more addressable bytes than the controller understands, the best outcome is that only the lower portion of the RAM is used. However, because of the way memory is constructed, it's also possible that the larger memory won't work at all.

    For simplicity, let’s consider a motherboard that has 16 address lines and an 8-bit data bus (meaning that a maximum of 64kB of memory is accessible. Let’s imagine that a 128kB memory device is installed. Now, it will have 17 address lines. Typically, within the memory device, address lines have a pull-up resistor on each address line, which means that if any address line is not controlled by the motherboard, it will be pulled-up to a high voltage level, or logic 1. Now, since the motherboard does not control address line 17, it will be held at logic 1, which means that the motherboard will actually access the top half of the memory device from address 10000(H) to 1FFFF(H). The memory from 00000(H) to 0FFFF(H) will never be accessed. As far as the motherboard is concerned, it will “think” that it only has 64kB of memory installed. This situation remains true, for every case where the installed memory exceeds the accessible memory space.
  4. #4
    A College Professor Naturally Camouflaged [your moreover breastless limestone]
    https://www.brighthub.com/computing/hardware/articles/79382.aspx
    Says it depends on the memory controller's ability, and that the memory controller can be either located on the motherboard as part of the northbridge or built into the cpu.

    http://www.cpu-world.com/Sockets/Socket_1150_LGA1150_H3.html
    Suggests the memory controller is part of the CPUs that fit the socket I have

    https://ark.intel.com/content/www/us/en/ark/products/80811/intel-core-i5-4690k-processor-6m-cache-up-to-3-90-ghz.html
    Intel says the processor I have can support 32GB

    I think I'm gonna try 32jiggs
    The following users say it would be alright if the author of this post didn't die in a fire!
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