Installed 32GB RAM and laptop won't boot

The maximum memory is often for all banks of memory being fitted. That would be 4 slots worth of memory so 4 x 8GB, the fact that laptops often only have 2 slots is irrelevant.

To explain; the processor will have 2 banks of memory and allow two DIMMs to be on that bank. They will then use a "chip select" line to select a DIMM within the bank. This allows them to cut down on the number of address lines coming out of the processor while still allowing the use of more memory.

If your laptop had 4 DIMM slots I would expect your 32GB to work as 4x8GB, but not necessarily 2x16GB as there may not be enough address lines going to the DIMM slots.

To clarify, what this means for a processor claiming to support 32GB (for example an Ivy Bridge CPU) is that it is most likely to only support 8GB DIMMs. This give the CPU its max RAM of 32GB in 4 DIMMS, and it is not likely to be able to support 16GB DIMMs.

From Wikipedia:DDR3

The DDR3 standard permits DRAM chip capacities of up to 8 gibibits, and up to 4 ranks of 64 bits each for a total maximum of 16 GiB per DDR3 DIMM. Because of a hardware limitation not fixed until Ivy Bridge-E in 2013, most older Intel CPUs only support up to 4 gibibit chips for 8 GiB DIMMs

That citation carries on to say that AMD supports 16GB DDR3 DIMMs just fine.

A newer CPU, such as a Haswell or later, CPU would definitely be able to support 16GB DIMMs (4 x 16 = 64).

UPDATE - this explanation came from the vendor:

The main problem is that the MRC (memory reference code) - which is part of the BIOS - does not support modules based on 8 Gigabit DRAM components (16GB modules consist of 8Gb components).

The MRC code reads out the memory-modules SPD-settings and finds that this module is using DRAM-chips with 8Gb capacity. Next it tries to look up the settings for the memory-controller in a table, but can not find any entries for 8Gb chips in the table.

As a result, it crashes.

If the MRC-software was modified - which nobody seems able to as the code is Intel proprietary and difficult to understand - your Ivybridge eventually might boot.

The next hurdle is a hardware limitation inside the CPU (can't get past first hurdle so this second hurdle is theoretical). Intel has said the hardware is missing in Ivybridge as well as most Haswells. Support for 16GB per module begins with 5th generation CPUs (broadwell).

I had a similar issue today and managed to solve it by manually setting the RAM frequency and voltage.

Thought I'd add it here in case it helps anyone.


My hardware:

Motherboard: GA-Z68XP-UD3
CPU: i7 2600
New RAM: 4x CT102464BD160B

Steps I took:

  1. Installed new RAM:
    System wouldn't boot to bios, fans spun for a few seconds and then system rebooted
  2. Tried each RAM stick individually:
    Still wouldn't boot
  3. Installed old RAM:
    System booted fine
  4. Updated BIOS, installed new RAM:
    Still wouldn't boot
  5. Installed old RAM, reset BIOS (battery out for several minutes, checked BIOS date was reset), installed new RAM:
    Still wouldn't boot
  6. Triple checked that the Motherboard and CPU would support the RAM:
    Yep, it does
  7. Cursed manufacturers, questioned sanity:
  8. Installed old RAM, manually set RAM frequency to 1600MHz and voltage to 1.35v in BIOS, installed new RAM:
    System booted fine - woOtz!!

Sure enough, when I looked at the BIOS, something between it and the RAM was incorrectly reporting the RAM as having a frequency of 1867MHz and voltage of 1.5v.