Current configuration
My laptop is capable of supporting up to 32 GB.
I presently have 4 slots filled with the following memory:
Samsung 4GB PC3-12800 DDR3-1600MHz non-ECC Unbuffered CL11 204-Pin SODIMM 1.35V Low Voltage Single Rank Memory Module Mfr P/N M471B5173BH0-YK0
RAM 16.0GB Dual-Channel DDR3 @ 799MHz (11-11-11-28) Memory slots Total memory slots 4 Used memory slots 4 Free memory slots 0 Memory Type DDR3 Size 16384 MBytes Channels # Dual DRAM Frequency 799.1 MHz CAS# Latency (CL) 11 clocks RAS# to CAS# Delay (tRCD) 11 clocks RAS# Precharge (tRP) 11 clocks Cycle Time (tRAS) 28 clocks Command Rate (CR) 2T Physical Memory Memory Usage 26 % Total Physical 16 GB Available Physical 12 GB Total Virtual 32 GB Available Virtual 27 GB SPD Number Of SPD Modules 4 Slot #1 Slot #2 Slot #3 Slot #4
Question
If I add a single module of 8 GB that is marked "dual rank", will the system work or not? In other words, if I make the configuration:
8 | 4 | 4 | 4
will it affect the functionality of the memory in the other slots?
Best Answer
Most CPUs support a limited number of memory ranks.
Most consumer DIMMs are dual-rank (this is the most economical solution).
However there are also single rank DIMMs and quad-rank DIMMS. The difference betyween these is rather technical (and I had to look it up myself about a year ago), but it seems to come down to this:
This is the rank.
This (https://serverfault.com/questions/69612/dimms-single-vs-double-vs-quad-rank) might be interesting reading to grok the background.
But to answer your question:
That simple is not enough information. To answer it with any certainty we need something like:
My best guess it that it will work.
Depending on he chipset you may and up with:
8GB DIMM 4+4) First part of the 8GB DIMM Only in dual channel mode 4GB DIMM (4)
4GB DIMM (4) In dual channel mode 4GB DIMM (4)
Or with no dual channel mode at all for 12GB of your memory.
Note that the ranks at this point are mostly about 'will it work', and the channels are about 'will I get the 5% average speed increase from going dual-channel`.