1

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 :-)

Improve this question
6
  • 1
    You wouldn't need to decide between DDR3 and DDR4. All current motherboards support DDR3 or DDR4, not both.
    – ChrisInEdmonton
    Commented Oct 29, 2014 at 14:51
  • 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
    Commented Oct 29, 2014 at 14:59
  • 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
    Commented Oct 29, 2014 at 15:12
  • What makes you think your computer will only use a second module when the first has been filled?
    – Mixxiphoid
    Commented Oct 29, 2014 at 15:19
  • 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
    Commented Oct 29, 2014 at 15:25

1 Answer 1

Reset to default
0

Memory management is handled by the operating system.

The memory management function keeps track of the status of each memory location, either allocated or free. It determines how memory is allocated among competing processes, deciding who gets memory, when they receive it, and how much they are allowed. When memory is allocated it determines which memory locations will be assigned. It tracks when memory is freed or unallocated and updates the status.

As per Ramhound has said, there are obvious gains in DDR4, specifically better performance and lower power consumption. In terms of performance, those gains will be highly dependent on your usage. Unless you use highly specialised software, you're not going to get a lot opting for DDR4 memory.

Improve this answer
1
  • Thanks, thats the info I was looking for. I was convinced that the hardware MC would do this. Of course will DDR4 be faster than DDR3 if you compare module vs module. But it is a difference if you have e.g. a increase of 2 or n*2. It was not to me clear how to exploid the advertised bandwidth increase. Because this is more a "game changer" than the know bandwidth increase already known from the past DDR generations.
    – westranger
    Commented Oct 30, 2014 at 14:34

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .