asymmetric memory (2GB + 4GB)

So,
I see that manufacturers are including 6GB RAM configurations with this mismatched (by amount) of RAM. Obviously, it must be fine but I have always believed that it is best to match memory... 2X2GB, 2X4GB, etc. I don't know if I want to go to the 8 GB level.

6 or 8 GB seems overkill, but I run some statistical analysis progs that are real memory hogs. STATA requires the user to set the memory dedicated to it at each session and some of my data sets are nearly 1.2GB. I also have large SAS datasets.

I am thinking of a Clevo M770CUH barebones from rjtech and assembling myself with my own memory, HDD, etc.

SO... as long as all specs match, 2GB + 4GB is cool?
Thanks
Tony

 

Yup, 4+2gb is fine

 

It will be slightly slower than 8GB symmetric.

 

Slightly. As in, it'll only show up in memory benchmarking software and will have no perceptible performance in other benchmarks. It's not like the old days of DDR and having to match DIMMs

That said, given the OP's statements of 1.2GB data sets, I'd highly suggest going with 8GB of RAM. 1.2GB of data on-disk has a way of greatly expanding in memory... you'll need as many resources as you can get.

 

There is a huge memory bandwidth hit by using asymmetric dimms do to it being single channel vs dual channel. However, this isn't an issue these days because increases in memory bandwidth have grown so much more than processing power that the extra bandwidth of dual channel provides no benefit most of the time.

 

No, there's not. There's almost no difference between dual and single channel operation: http://www.tomshardware.com/reviews/PARALLEL-PROCESSING,1705-12.html

Definitely way less than "huge" bandwidth hits. < 10% on the most favorable synthetic test, hovering at maybe 1% or so in actual application tests.

 

Although in theory it should be no problems, I did have problems mixing memory of different size in my Dell Latitude E6400. had a 1gb and 2gb module (3gb total) of the same speed (DDR2-800mhz). It worked fine most of the time, but would get video corruption every few hours. (it had intel integrated video that uses the system memory).

Running windows xp, vista and 7, every few hours the display will be completely distorted (random colors/patterns all over the screen), have to refresh the display, and sometimes reboot the system to fix it.

The problem went away when I upgraded to 4gb of memory (2x2gb).

I don't know if this was isolated to the E6400 or not. I'm running 3gb right now in my mother's Dell Studio 14Z and have no such problems, although it is not using intel integrated video, it's using a nvidia gpu.

My wife's Latitude D620 has also been running on 3gb of ram for a few years now and have no issues.

I was able to reproduce the video distortion on a few of my co-worker's E6400 using also 3gb of ram.

 

The problem was more than likely the Intel integrated video. The drivers and hardware have long been sub-par on Intel video chips. Windows and all motherboards should be able to handle mismatched DIMMs fine.

 

There is no huge bandwidth hit by using asymemetrical dimms because the chipset will use asymmetrical dual channel mode which is almost the same as regular dual channel.

 

Isnt it about time for triple channel ram to hit laptops?

 

add ", permanent" to the end of your set memory statement.

 

Yes, and no. Triple Channel requires a triple channel memory controller, and (assuming we're talking about Intel) that means that with the migration of memory controllers onto the CPU die, the only chips that support triple channel are the first generation Bloomfield i7 chips, the LGA 1366 ones. As a result of this, there is a notebook that supports triple channel; the D900F, which just happens to use the previously mentioned family of i7s. All other i7 chips, (and C2 CPUs, which use a northbridge dual channel memory controller) are limited to dual channel, due to the memory controller on the CPU die (or northbridge for the C2s) only supporting dual channel.

 

It'll also need more RAM slots and therefore larger machines as well. Multi-channel memory controllers have been much less of an impact that just moving the memory controller onto the CPU.