Memory Question

What's better? 2 sticks of 4GB or 4 sticks of 2GB (assuming frequency is the same, Manufactuer, and other system specs.)

I've always wondered if this has had an affect on performance, but could someone please tell me the advantages & disadvantages/Pros & cons of using one over the other. Price is not important because i'm not building,

If your mobo has four ram slots I would get two sticks of 4gb just so you could upgrade in the future.

Two sticks would be better. For one, you have more expandability down the road, but the real issue is that you're going to get a better overclock out of your CPU if you're not using all of your RAM channels.

ok, so this is actualy a fairly complex question. assuming you have a dual channel memory mobo, it would be better to install two 2gb sticks instead of a 4gb stick. as you would have more bandwidth for memory. the performance between 2 and 4 sticks would be the same, as with two sticks, you would have one stick per memory controller and with 4, you would have 2 sticks per memory controller. each configuration will use both memory controllers. however with one stick you only get one controller. now, the besst way to pick your memory, is to take your max ammount and devide that by ammount of dimms. (ie, if you have 4 slots and you can have a gax of 16gigs, you take 16/4 and get 4. so buy 4 gb sticks.)


i did a post on my blog about ram in general. since your asking questions like this im sure you will find it interesting. clicky

basicaly explains timings and such.

WOW, that really is complex.

So will one increase gaming FPS? if so which one?

no. to be honest, ram does not play that big of an impact in fps. the best way to explain ram is from a programming stand point and apply it to gaming.


say for example i want to record someones position on a map in an x, y and z. i would create 3 variables (names x,y and z) then i would store their position in these variables. the cpu will alocate three 32 bit inteagers in ram, and then set the bits to equal the values i gave it. this has nothing to do with whats being rendered on the screen. instead, that is video memory. with video memory, the gpu's shader units compute the 3d game word and all the textures and how they should be rotated and applied to models. it then says "hey, what is the 2d image this would make?" it computes what each pixle should equal (rgb) and then saves that to video memory. now, lets assume you are gaming on a 1920x1080 screen. thats 2073600 pixles. the way colors work, is you have 8 bits for red, green, and blue (28 bit color depth) with 8 bits for your alpha (which is not used for display, but is used for internal calculations) so lets do a bit o' math... (((2073600*28) / 8) / 1024) / 1024 = 6.921 MB per frame. so each frame needs 7 megabytes of data just to display the image on the screen. now in most game engines you have at least 2 or 3 frames pre rendered ahead of time, so 21 MB of data for display. this is not counting the data that is needed for all the textures and shader data. so why does this matter? well, the larger the screen area, the more data is needed for ALL of that, which is why you need lots of video memory for multi screen setups.

so why exactly do you need lots of system ram? say i load a game, all the non video data is going to be stored in system ram. this includes your health, ammo, kills, the ip addresss of the server your connected to, the buffer for all the network info being sent to and from the game, sound files, the map itsself, ext... so what happens if you have 2 gigs of ram, a gig of opperating system loaded into it, then the game loads a gig and a half of info? well, you cant get rid of the OS. and you need the whole game in ram to run right? so windows will put a gig of game into ram, then shit the other half gig into the paging file. incase you dont know what a paging file is, its a section on the hard drive that is reserved for 'virtual memory'" basicaly windows will put the data that SHOULD have gone into ram there, then swap that to and from ram when needed. well, hdd's are slow so guess what? now you have bad game performance.

in other words, the main performance hit is not having enough ram for games, NOT the ammound if ram dimms you have flled.


now, lets see, if you are doing non gaming (like number crunching on the cpu - which is stupid, now with gpu compute coding libraries) ram does come into play. if you read the post i made, you will know about timings, so doing lots of fetches, lower timing is important, as you are wiating for lots of precharging and waiting. so why does frequency matter??? say you have to wait 9 cycles for a strobe to read (9 cas). at 1333 mhz thats .0067 seconds (6.7 ms). now, lets see what that would be at 1600. after that calculations we find a cas strobe will be a delay of .0056 seconds (5.6 ms). however, low quality ram does not like to run at cas 9 at 1600 mhz. so instead you have to up your timings. usualy 9-9-9-27 ram has to be switched to 10-10-10-30. so at 1600 mhz you will see a cas strobe is .00625 (or 6.25 ms) so you can see that by oc'ing your ram, even though your timings are worse you still get a tiny tiny increase of speed ( .45ms).

so yeah. there you go. thats ram in a nut shell. the difference between 1 or 2 memory controllers is like, nothing. like 1.5% difference (,1705-11.html)

so why IS there dual channel ram??? well, there is a bottle neck between cpu's and memory controllers. cpus got faster, and mem controllers could not keep up (due to command rate limitations, and how many qwords are being sent per cycle... blah blah blah) anyway, in short... you add another memory controller, and bam! all of a sudden you removed that small (like rly small) bottle kneck.

also, good questions warrent good answers. lazyness (like asking me to make you a pc under a certain budget without doing any research yourself) results in me skipping your post. thanks for posting a good post... :)

faster ram only makes a difference with an APU, as the system ram is also your video ram



yeah, agreed ztrain, definately gonna spend more time on someone who poses a good question, or put together something themselves and is looking for someone to check it over, rather than having someone build it for them



and since commissar bought up a good point with the APU's ill go ahead and explain why as well. the APU is a special child. since it has a gpu built in, it doesnt have much video memory built in (it has some cache memory, which is used by the ALU's and shader units for calculations, as it is faster then ram) however it uses system memory as the video memory. that means if you have 8 gigs of system ram, that will be shared between the cpu and gpu that are located on the APU. now, a lot of people are like "zomg, you cant get gddr5 system memory, so the ram will suck!" well, what most people dont know is gddr5 is just ddr3 ram with an added 8 bit look ahead buffer. so, ddr3 is fine. and as i said above, higher clock speeds = less time between value read / writes. so yeah... if you have a 1920x1080 screen we are talking 7MB of data per frame. so at 60fps thats 420 MB of data a second being written from the ram to the screen.... so speed is NEEDED LIKE WATER IN THE DESERT! lol....

wow, didn't know that about gddr5.... interesting yep. interesting stuff. cant wait to get my degrees so i can be working with this shit daily....

iGPUs need the fastest ram you can get with the lowest latencies. I have 1866mhz Cas 9 and if you were using something like Virtu MVP which is integrated graphics helping out dedicated graphics with some rendering, then yeah I would strongly suggest fast ram. Even faster than I have.

i GPUs crave speedy ram.  

To answer your question more precisely, check out your MOBOs memory controller and see what's on the list of TESTED vendors for RAM. You probably only want 2 sticks of 4GB and since it's like $30-$50 for decent speedy ram, you shouldn't have to worry too much about cost. Get the 1866 Cas 9 latency RAM but don't get 1866 Cas 11 latency or you'll hate yourself later. 2 sticks of 4GB seems to be the most widely used format for optimal perofmance and compatibility with modern motherboards.