Well, we need to what type of system you are talking? I7-900 series are the only cpu's that do triple channnel, which requires 3 sticks, 4 sticks will make it run in dual channel mode. All others run in dual channel when using 2-4 sticks of mem and if you use 3 sticks will run in single channel, unless you can ungang the memory. Other than that, that is it.
you dont have to know what kind of cpu, because when i said triple then u have to know its a motherboard that supports triple channel, in our case X58 motherboards as of now yet, thats why i didnt mention what kind of cpu, because some others might have triple channel in the future, might be for amd as i dont know much about amd.
@surda - How the memory controller reacts to memory that's not evenly distributed across the channels depends on the memory controller. Some of them require the memory to be evenly distributed and others don't. So the answer is: consult the manual.
@Twoboxer - it's not about speed, it's about parallelism and throughput. The speed that the RAM operates at has nothing to do with how many channels there are. If you have two channel memory that operates at speed "X", then the throughput is 2X because you have two of them operating at the same time. But the speed of each is the same, and the speed doesn't change if you remove one DIMM.
It's like saying that cars which travel at 60MPH can drive in only one traffic lane or in two traffic lanes. The speed is the same in both cases, but with two lanes you can move twice as many people per hour.
straight from intel "Memory Configuration for Dual Channel Mode: Dual channel mode can be achieved with two, three or four DIMMs."
essentially channel a must equal channel b
so if you put 2 sticks of 512MB into channel A, and then 1 stick of ram of 1GB in channel B, then this will still allow dual channel to function
Of course, the OP's question revolves around 3 sticks of the same RAM which would indeed not work and make all 3 run as single channel.
The following conditions do not need to be met:
* Same brand
* Same timing specifications
* Same DDR speed
therefore the most important thing is the balance of ram density/size
I've read the same thing on other boards that the most important thing for dual channel is the SIZE....but not matching the timings or SPEED will cause you to function at the worst dimm module (so you end up limiting your good ram)
1.) all would run in single mode
2.) dual channel mode
3.) single w/ stipulations for dual
instead of the questions only, what specific motherboard are you questioning about; LGA1156, LGA1366, LGA1155 (SB).?
I doubt were talking about AMD unit are we.?
DO NOT MIS-MATCH RAM...
AMD uses something called an IMC (Integrated Memory Controller).
It helps the AMD chips perform very well in memory related tasks (because now the ram isn't controlled by the motherboard through the FSB)
but it also has a few quirks.
The IMC doesn't seem to like a lot of stress, and so in general, you wont get as much of an OC out of your ram if you have all of your ram slots populated.
So it should be easier to get more performance out of only two sticks of ram.
*Intels Nahelem architecture utilizes this same design, leaving the Core 2 series as the only mainstream processor to still use the FSB design.
Also, the same thing goes for mismatched ram, the IMC just doesn't like it.
So if you have ram that is not from the same kit, and are experiencing instability, try taking out the non-matching set, and see if that helps out.
Also, you might have heard about the “timings” of the ram, and how that is important.
I have seen a lot of people get confused with that.
Let me explain this as simply as I can.
There is memory speed, and then there are memory timings.
Speed is the frequency that the memory operates at (in MHz... and remember that when you are looking in CPU-z that ram is DDR [Double Data Rate], so the frequency that it says will always be half of what it is actually running at). It is fairly straightforward and easy to understand.
And remember that the ram speed is tied to the reference clock, and in this way you can easily OC your ram beyond the stock speed.
Speed is mostly important for higher bandwidth, as it just means that the ram can move more information.
Timings are different, and should not be confused with the speed. Timings do not effect the speed (in MHz) of the ram at all.
Instead, they change how “efficient” the ram is. In other words, the timings affect the “turnaround” of the information.
The timings are generally listed something like this: 5-5-5-18. While I wont go into all of the details about what those each mean here,
I can give you a basic idea of what the timings mean. Timings change how long the ram will wait to do something.
So having ram with looser (numerically higher) timings, means that the ram will “wait” longer in between processes.
Using the example of 5-5-5-18 ram, information is copied, it then waits for 5 clock cycles before it moves onto the next step.
Ram with 7-7-7-23 timings running at the same speed (in MHz) will move the information there just as quickly,
but then will need to wait for 7 cycles between doing things, rather than 5.
This is why “performance” ram is in fact faster.
+1 but sminlal also has an extremely good point. Consulting the manual would be best. Aside from SC and DC modes, there exists Flex Mode. Intel based boards can use both SC and DC modes simulatenously. This happens when the all of the installed RAM does not meet the criteria for DC mode, such as having three sticks installed. Since we're all 'assuming' that the DIMMs are identical, OP...
1. Could either be all SC mode, or in the case of Flex Mode, 2 sticks in DC, 1 in SC.
2. DC mode
3. Why the hell would one even consider this? -- DC mode, though, unless the stipulations for Flex mode exists, then possible TC and SC mode.