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My laptop PC has an Intel-Core-i7-620M CPU. Now, I want to upgrade the RAM from 4GB to 8GB. I checked this website to check the compatibility.
http://ark.intel.com/products/43560/Intel-Core-i7-620M-Processor-4M-Cache-2_66-GHz
it says that the CPU can support up to 8GB, but I don't know whether it is a single 8GB, or 2 separate 4GB RAMs because my PC currently have 2 separate 2GB RAMs on each slot. For you information, I also attach some pics below:
Either will work, however 2x 4GB sticks are recommend as this will double the available memory bandwidth to the processor as the processor will use both memory channels. Don't listen to people like Ramhound who say that it is determined by the chipset. The memory controller is located on the processor for the Core i7 series chips, and has been on most consumer laptop/desktop processors for years now.
The information provided in OP question is insufficient. Information in the Intel database,
"Max Memory Size (dependent on memory type) 8 GB"
is confusing, but might contain a clue with qualifier "dependent on".
If the User documentation and Qualified Vendor List is not available for the particular laptop, you can examine similar products designed around the mobile chips as i7-620M, e.g. HP Elitebook 8540W workstation. The page says regarding the supported memory:
"Maximum: Upgradeable to 8192MB with 4096MB SODIMMs in slots 1 and 2"
This pretty clearly indicates that the max limit can be achieved only at 2 x 4GB configuration.
So, the background logic is this. Memory capacity is determined by address space times memory width. If the memory has dual channel architecture (2 x DIMMs), and advertised limit is 8GB only, it means that each channel is limited to 4GB address space. Therefore, a 8GB DIMM memory can use only half of its space, since there is simply not enough address lines on the CPU/board side.
If a CPU could support an extra address line (making it 8GB per a channel), there should be no difficulty to support 16GB per CPU, which is not the case. Therefore, the address limitation for this CPU is 4GB per channel, and a 8GB stick will either run at half capacity, or likely will not run at all, due to BIOS confusion with memory SPD and likely an absence of corresponding entry in memory configuration table.
How the question: why would you risk and use questionable memory configuration instead of taking no risk and go with known configuration? If you already have the 8GB stick, just try it, it will not harm the laptop physically. The only side effect could be in BIOS confusion and possible security lock related to perceived tampering with memory size. But this state of BIOS can be reset to defaults. Is this your real problem?
