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I'm a bit confused about how DDR4 works in detail. I'm not very familiar with DDR details or Memory-Controller details. So far DDR4 is advertised everywhere that the transferrates of DDR4 accumulate with every module which I have on my board. For example if I have 4 modules each with a capacity of 4GB and let's say 20GB/sec. I would end up with 80GB/s transferrate with 4 banks filled. In my opinion this works only if I have an application which uses the whole 16GB of RAM. But how fast can the transferarte be if my application uses only 2GB.
Will there be some internal logic which distributes the 2GB equally to all 4 banks? If so, who does it?
My point is: e.g. if I need to decide between
- a DDR3-2133 which has 16GB mabe up of 2 modules
- a DDR4-2133 which has 16GB made up of 4 modules
lets assume the prices are the same but the timings for the DDR3 are much better than the of the DDR4. The transferrates per module are the same. If the data which is allocated by an application does not exceed the capacity of a module and is not distributed equally to the other modules the DDR3 would be the better choice because the timings are better and the DDR4 would not yield any advantage right?
The best literature which I found was this but is does not tell much about how the memeory is managed
I hope someone here can shed some light on the details :-)
1You wouldn't need to decide between DDR3 and DDR4. All current motherboards support DDR3 or DDR4, not both. – ChrisInEdmonton – 2014-10-29T14:51:01.507
For me it's more about the transferrates and if DDR4 really yields so much perfromance or if it is just in the case that the RAM is fully utilized. If it is application dependant or not. – westranger – 2014-10-29T14:59:00.080
In the end this would influence the buying decicion. If only applications which fully utilize the RAM benefit from DDR4 one should try to buy many small modules for a desktop system but if these are not available at the market DDR4 would be inferior to DDR3 in the desktop sector (at the moment). – westranger – 2014-10-29T15:12:05.637
What makes you think your computer will only use a second module when the first has been filled? – Mixxiphoid – 2014-10-29T15:19:32.070
I don't know :-). This is actually my question, how is the data distributed if an application allocates memory? And is there some logic which tries to exploid the befefits of DDR4 – westranger – 2014-10-29T15:25:05.400
16GB of DDR4 will out perform the fastest 16GB DDR3 memory by several factors. Nothing else matters. It does not matter how the memory is managed.....from a user perspective. – Ramhound – 2014-10-29T16:04:30.547