I own a Dell Vostro 2520 which came with an Intel Core i3 processor and 2GB RAM. I never noticed the RAM frequency before adding RAM. I thought of adding 2GB RAM as my laptop had a second unused slot. After adding when I checked the config in BIOS, it showed that my RAM frequency is 1600 Mhz. Both of my RAM are of 1600 Mhz. But Speccy shows that my DRAM frequency is 665 Mhz. I know we have to multiply it by 2 because of Double Data Rate. But again it's lower than 1600 Mhz. Why is it so? Is it because of differing RAM voltages (1.5 V and 1.35 V)?
RAM running at a lower frequency
cpumemorymotherboard
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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).
Best Answer
Most likely it's 666Mhz (1333MT/s). Some processors are not capable of 800Mhz (1600MT/s). The 2nd gen i3 processors in the Vostro 2520 (and most other 2nd Gen core i CPUs) do not support 1600MT/s, only 1333MT/s.
An example, the i3 2328M from a Vostro 2520:
http://ark.intel.com/products/70927/Intel-Core-i3-2328M-Processor-3M-Cache-2_20-GHz
Some 3rd generation and later CPUs support 1600MT/s though.
Also note the "multiply by two" has nothing to do with "dual channel mode". The multiplying by two occurs because it's DDR RAM. DDR stands for double data rate.