What is the required conditions for Dual Channel RAM ?

There is a laptop Thinkpad T431s with a soldered 4 GB RAM, but it has one free slot RAM. Let's say the soldered 4 GB RAM is DDR3 PC3-12800 (16000 Mhz) CL 11 Hynix brand. So to enable dual channel RAM for the laptop, is it correct that I should add another 4 GB RAM with same brand, same PC/Mhz, and same CL? Or is there something I miss?

 

Yeah, you got the right idea.

If your RAM wasn't soldered on; I would suggest to replace both modules with identical Sodimms to ensure stable, fast and optimum performance.

(Once verified/tested that the new RAM is fine; you can always sell the one off module you removed - if removable, of course).


Good luck.

 

If the new RAM has not same brand but it has same PC and same CL, could the dual channel still be enabled? Is there a software that I can use to check whether the dual channel is active or not?

I'm worried because the brand from manufacturer (such as: hynix, ramaxel) is not easy to find.

 

Yes, it will/'should' be enabled. But the 'exact' matching will ensure that no funky interactions from differently spec'd Sodimms will plague your system.

For the small cost of a single 4GB module; I might be tempted to pay full Lenovo prices (to ensure max compatibility).

If your dependency on your system is not as critical as mine: take your chance with the Sodimms that are available to you locally.


Good luck.

 

I'd also recommend buying the notebook with the extra RAM installed - maximum compatibility as noted, plus it will be covered under warranty along with the rest of the notebook.

As an FYI - if you installed a slower (MHz) RAM chip, the faster one would slow down to match its frequency.

 

The RAM comes with it's own warranty too, guys. So if OP buys RAM aftermarket, there's still the option of taking the RAM back for repairs/replacement in case something happens to it. And it's not like adding your own RAM will void anything; hell, the IBM tech that came to my house a few weeks ago saw the Mushkin aftermarket RAM (and my aftermarket SSD) along with the factory 4GB Samsung stick and he couldn't care less. The only reason I'd even bother paying Lenovo's (or anyone else's) full retail (over-)priced RAM would be if I wasn't competent enough to replace it myself for much cheaper.

As for matching brands, it's nice to do but definitely not required. Never had any problems with my setup in the past two years, and counting. Dual-channel works for two of the sticks, but not all since I have an odd number (3).

 

Thanks guys. I asked this because there are many informations about dual channel requirements. From this article, the requirements are:

• the same module capacity in pairs (2 x 128 MByte, 2 x 256 MByte, 2 x 512 MByte, etc.);
• the same DRAM technology (2 x 256 Mbit or 2 x 512 Mbit);
• the same DRAM bus width (x8 or x16);
• single-sided or dual-sided modules must be used in pairs;
• memory slots must be fitted symmetrically (first Channel A, Slot 0 and Channel B, Slot 0, then Channel A, Slot 1 and Channel B, Slot 1).

The fifth can be ignored as there are only two slots in T431s. What I don't understand is DRAM technology and DRAM bus width. How to make sure the new added RAM has same DRAM technology and bus width?

Wikipedia also mentions of "Number of chips and sides" and "Matching size of rows and columns". Other forum also mentions both RAM must have same timing.

For example, I added one ram to my Z480:

Slot #1: (I added 4 GB corsair RAM with CL9)


Slot #2: (this is the innate 4 GB hynix/hyundai RAM from the laptop, I believe the CL is 11)


Is this configuration valid for enabling dual channel ?

 

Having asked the same thing in another thread, I have just upgraded my PC12800 16000mhz CL11 RAM with different brand and the dual channel works well. Although one is 11-11-11-28 the other one is 29 according to hwinfo software monitoring No BSOD, Hiccups, or symptoms to unusual behaviour lol.

 

Correct about the warranty on aftermarket RAM; consider though that Lenovo's turnaround time in the event of an issue would likely be much faster.

My experience says that the RAM manufacturers install in the factory is held to a very high quality standard - I've yet to see an error in memtest86+. Approximately 50% of the RAM I've purchased aftermarket over the last 7-8 years (desktop and notebook) has required RMA due to errors. I now pay the extra to get factory-installed RAM for this reason.

 

How did you know the dual channel is working? Is there software to check this?

 

Ram are ram, throw w.e ddr3 in it, it will run in async dual channel, put any 4gb,it run in will in real dual channel.
Standard exist for some reason.

 

Hwinfo Great monitoring software :thumbsup:

 

CPU-Z is another great tool to figure that out.
CPU-Z CPUID - System & hardware benchmark, monitoring, reporting

Here's a screenshot from my notebook.

 

Thanks. I read some pages that said dual channel can be enabled even if the two RAMs are not in same size. For example in T431s, I will add 8GB RAM so total is 12GB (4GB + 8GB). Is that true?

 

IIRC, yes, that's true, but only the first 4GB of the 8GB stick will be dual-channel(?).