DDR3 question

Hi guys

I purchased an XPS 17 l702x with the 3D screen and 3GB graphics card so it comes with 4 memory slots. The laptop came with a 4GB and 2GB stick of RAM installed.

So I've decided to upgrade the memory as it's quite cheap and can't hurt so I've been reading around. I've been reading that the RAM needs to be installed in pairs for optimal performance. So I'm confused why mine came configured with a 4 and a 2???

Anyway, I guess my question is can I get away with just buying a pair of 4GBs to put in the spare slots or should I replace the lot?

How much real world performance difference would not having the RAM in pairs make?

Thanks for the help
Ash

 

2-5% Synthetic (benchmark) performance difference and close to zero in real world (except if you were using an igpu solution...).

I would suggest to replace the lot with 4x 4GB modules - test these overnight with a good memory checker and then sell/give away your original 6GB modules.

Any lifetime warrantied DDR3 RAM module you pick (just go by price) is good enough).

Why did your's come with 6GB (no such thing as a 2x 3GB setup, btw...)? Because Dell probably had about a half million 2GB sticks laying around and had to get rid of them somehow.

Good luck.

 

you want to keep ram in even numbered pairs to keep it in dual channel...so 2x2, 4x4, 8x8 etc

4x2 is semi dual channel...the memory controller is smart enough to keep the first 2 gigs of the 4 gig stick in dual channel (running it dual with your other 2gig stick) and the remaining 2 gigs will be run in single channel.

i don't know what the numbers are on a modern memory controller, but 4 years ago, i benched 8% more 3dmarks in dual channel and games increased 3-4% so it was significant

The most economical upgrade for you is to get a 2 gig and a 4 gig stick of ram...then pair them 2x2 in slots 1,2...and go 4 x4 in slots 3,4 for a total of 12 gigs of ram. You will be in dual channel

 

Thank you for your help. I appreciate it.

Just wanted to know why you would suggest replacing the lot if there's not much performance difference in keeping the old ones. Also, can you please suggest a memory checker to use.

Cheers

 

i've always used the tried and true memtest86 to check my sticks

 

That's a good idea. I didn't think of buying a 2 and a 4. Would there be a problem in using different brands like a dell 2gb paired with a crucial 2gb? If not then I think that'll be my solution. 12GB total is more than enough

 

As long as the sticks have the same specs (i.e., they have the same speed [1333/1600 etc], timings, and they are at the same voltage like 1.5v's) you can mix and match without issues

The stock ram in the dell are usually hynix or samsung which has good compatibility with crucial, but you should open up the back plate and take a look at what kind you have.

 

Cheers. I will check it out

 

yeah ... no wonder mine came with four 2GB sticks..... stupid DELL
anyway samsung new 30nm RAM is avaiable yet??? if it is then it might be better idea to go for that one.....

 

Thanks for the help guys. I've ended up ordering a 2GB and a 4GB from crucial as the specs seem the same as the ones installed in my laptop.

Just another question. When I opened up my laptop and looked at the memory installed there were 2 sets of 2 slots. The 2 memory sticks already installed in the machine were in different sets occupying the bottom slot. When I install the new memory am I right in assuming that each pair sits on top of each other i.e. 2x2GB in the same bank and the 2x4GB in the other bank?

And finally, how would I test the memory to make sure its actually installed properly in dual channel mode??

 

Download CPUz.

See:
http://www.cpuid.com/softwares/cpu-z.html


Check if you are currently running in Asynchronous DC mode.

See what slots are currently used - I would guess that the 'bottom' slot in each set would be the ones the 4GB SoDimms would be put into.

The 'top' slots would be for the second, or 2GB SoDimms in your case.

When you get your new modules, I would try the 4GB slots in all configurations to confirm with CPUz that you are truly running DC mode - or - simply consult your notebook's manual for the proper installation of the 'main' set (usually the bigger capacity modules) in the right slots.

 

Sounds like a plan. At the moment CPUz says Dual in the Channels# field but the DC mode and NB Frequency are grayed out and empty. I guess I'll be expecting something in the DC Mode field if all's installed well?

ps I checked the manual which isn't very useful at all and it doesn't mention pairing.

link to manual

 

After studying the 'Replacing the Memory Modules' table in your link, I would say that it does indicate pairing - although the BIOS is able to 'fix' most mis-configurations automatically.

As you can see in the table, Slot A and Slot C are the 'main' memory module connector slots - with a single RAM SoDimm; the system will not boot with a single module inserted into Slot B or Slot D.

Also, since your memory modules are currently in different connector sets, I would say that you should be using the DIMM A and DIMM B slots. Can you see any markings that will confirm this inside or around (look at the access door you are removing too) the connectors? Or, maybe CPUz can help by showing which Slot# is being used by the 4GB module and which Slot# is used by the 2GB module.

To further check/test this: move the 2GB module to another DIMM slot and see if CPUz is reports that the RAM is running in Asynchronous DC. Move it either to the top slot in the different connector set, or move it to the same connector set as the 4GB SoDimm module.

I'm assuming that the 4GB SoDimm module is in DIMM slot A - can you verify?

When you get your new RAM sticks, it should/will be easier to see which DIMM slots (A + B or A + C) enable Dual Channel mode. Make sure you are only putting the two 4GB sticks to test this in the fewest steps possible. Then, the 2GB sticks will go in the other DIMM Slots (and be in Dual Channel too).

Also, remember to remove your AC power adaptor and battery before you insert/remove any SoDimm modules (or any other parts).

Good luck.

 

Thank you for taking the time to give a thorough reply. I don't think I'll open up my machine again until the memory arrives but here's a picture I found online of what it looks like. Slots A and B are in one bank and slots C and D are in the other.



I'm not sure if my 4GB came in slot A or not but the two definitely occupy slots A and C. CPUz confusingly states that my 4GB is in slot 4 and the 2GB is in slot 2!?!

I will perform the check to see if CPUz will report a different DC mode if I move the ram around. Is it possible that the mainboard is actually smart enough to configure the RAM optimally no matter what slots are used?

Cheers

 

Anyway, I decided to call DELL tech support and it was confirmed that the 4GB sticks should be installed in the bottom slots and the 2GBs on the top. Hope this may become useful for someone.

Thanks again for the help and info.