W530 dual channel

Question

I upgraded RAM on my W530 and it's working only in single channel mode. How to enable dual channel in BIOS?
Here is screenshot about my RAM
http://imgur.com/ilbCUil
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Answer 1

I did some testing earlier this year and did a short write-up and decided that the advantages of dual-channel, frequency and cas latency were more theoretical than practical. I was using a laptop with 2 slots, so it isn't quite the same, but it was an i7 Ivy Bridge CPU, so there should be more similarities than differences. This is what I wrote:
Probably more often than once a week, I see or hear a question regarding advantages of buying faster memory or using matched pairs of DIMMs. Obviously, using memory that is rated faster than the bus speed yields no improvement, and I always believed that advantages of "matched pairs" was more theoretical than actual. For no good reason, I decided to run a semi-scientific test. I have a T430s machine here, which will run at DDR3-1600 or DDR3-1333 mHz, depending on the memory installed. I also have 2 matched pairs of 8GB DIMMs. One pair is Corsair Value memory (DDR3-1333 CL-9) and the other pair is Corsair Vengeance, their "better" memory (DDR3-1600 CL-10). My idea was to test the memory 3 ways: 2 faster DIMMs, 2 slower DIMMs and mixing one of each type. My expectation was that the fast memory would run at 1600 bus dual-channel; the slow memory would run at 1333 bus speed dual-channel, and the mixed configuration would run at 1333 bus speed, but not use dual channel operation and be the slowest. First, I ran the windows7 "windows experience test". The faster memory gave a "memory operations per second" score of 7.6, while the slower memory gave a score of 7.5. The mixed option was the same as the slower memory. 
I then ran Memtest86+. (the free memory tester I use) First, it became obvious why the mixed set ran as fast as the matched pair of slower memory. The mixed set was using dual-channel operation. I now assume that "matched pair" really means any 2 of the same size. When I ran the full memory test, the faster memory took 1:20:45. The slower memory took 1:21:55. I ran one more test to look at single-channel vs dual-channel operation. I ran just one of the faster DIMMs. If it were running at the same speed, the test would have taken half the time taken by the pair, or 40:23. It actually took 41:52, and the windows experience score fell from 7.6 to 7.2. I was going to complete the test by running 2 4GB DIMMs, but the only PC3-1600 4GB DIMMs I had were the ones that Lenovo includes with systems, and it is slightly slower that the DDR3-1600 memory I used (CL-11 VS. CL10).
It seems clear to me that one would never be able to notice any difference in any real application, but there was a measurable difference that would allow someone to win a "mine is bigger than yours" contest