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Why do z97 boards max out at 8GB per stick?

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  • #1

    Why do z97 boards max out at 8GB per stick?

    Hi!

    I'm about to buy my next computer which I'd like to be built around an ITX board. This would however limit me to 16 GB memory, which feels quite constraining.

    Given that there are 16 GB unbuffered DDR3 DIMMS and the Haswell memory controller can handle 32 GB of memory, I'd really like to know where the 8 GB per stick limit is coming from, preferably with original sourcing? I'm having a really hard time finding any hard technical information on this issue.

    Thanks!


    Sent from my iPad using Tapatalk
    Tags: None
  • #2
    Re: Why do z97 boards max out at 8GB per stick?

    The horses mouth.
    #1 - Please, when seeking help, enter the make and model of ALL parts that your system is comprised of in your Signature, or at least the model #'s in your System Specs, then "Save' it.
    ____If you are overclocking, underclocking, or undervolting any parts, informing us of this and their values would prove beneficial in helping you.


    #2 - Consider your PSU to be the foundation from which all else is built upon. Anything built upon a weak foundation is poorly built.

    Comment

    • #3
      Re: Why do z97 boards max out at 8GB per stick?

      I prolly should've added I have my ideas. No technical knowledge to back it up though. An argument looking for a discussion.

      AFAIK, actual 64GB support using Intel procs, you'd currently be looking at the X79 chipset/boards.
      #1 - Please, when seeking help, enter the make and model of ALL parts that your system is comprised of in your Signature, or at least the model #'s in your System Specs, then "Save' it.
      ____If you are overclocking, underclocking, or undervolting any parts, informing us of this and their values would prove beneficial in helping you.


      #2 - Consider your PSU to be the foundation from which all else is built upon. Anything built upon a weak foundation is poorly built.

      Comment

      • #4
        Re: Why do z97 boards max out at 8GB per stick?

        The 8GB limit for each DIMM is an Intel spec for the Haswell CPU's memory controller:

        Click image for larger version Name: haswell memory specs.PNG Views: 1 Size: 51.1 KB ID: 754486

        Standard 1Gb, 2Gb, and 4Gb technologies and addressing are supported for x8
        devices. There is no support for memory modules with different technologies or
        capacities on opposite sides of the same memory module. If one side of a memory
        module is populated, the other side is either identical or empty.

        Seems to be an addressing limitation with DRAM chips beyond 4Gb (Gigabits).

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        • #5
          Re: Why do z97 boards max out at 8GB per stick?

          Thank you, parsec! That was precisely what I was looking for.


          Sent from my iPad using Tapatalk

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          • #6
            Re: Why do z97 boards max out at 8GB per stick?

            As explained on AF this is a BIOS limitation and not a hardware limitation.

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            • #7
              Re: Why do z97 boards max out at 8GB per stick?

              As explained on AF this is a BIOS limitation and not a hardware limitation.
              AF? Enlighten me about this please.

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              • #8
                Re: Why do z97 boards max out at 8GB per stick?

                As explained on AF this is a BIOS limitation and not a hardware limitation.
                Yea, I'd like to see where or who says it's a BIOS limitation on the Z97 too. I'm of the understanding as what paresc posted, that being the CPU and not the BIOS
                #1 - Please, when seeking help, enter the make and model of ALL parts that your system is comprised of in your Signature, or at least the model #'s in your System Specs, then "Save' it.
                ____If you are overclocking, underclocking, or undervolting any parts, informing us of this and their values would prove beneficial in helping you.


                #2 - Consider your PSU to be the foundation from which all else is built upon. Anything built upon a weak foundation is poorly built.

                Comment

                • #9
                  Re: Why do z97 boards max out at 8GB per stick?

                  Google fu: Why do Z97 boards max out at 8GB modules? - AnandTech Forums
                  #1 - Please, when seeking help, enter the make and model of ALL parts that your system is comprised of in your Signature, or at least the model #'s in your System Specs, then "Save' it.
                  ____If you are overclocking, underclocking, or undervolting any parts, informing us of this and their values would prove beneficial in helping you.


                  #2 - Consider your PSU to be the foundation from which all else is built upon. Anything built upon a weak foundation is poorly built.

                  Comment

                  • #10
                    Re: Why do z97 boards max out at 8GB per stick?

                    Nice find on that link wardog, and what AF means, OMG I would have never thought of that!

                    Hey, we're famous, this thread is now linked in the AF thread about this topic. The table I posted is given as an explanation for the limitation in the AF thread! There are several theories and a fact or two that all mixed together add up to... no clear conclusion at the time of this post at least.

                    We may not know why (the table I took from an Intel document is BS is apparently the implication of a post or two in the AF thread) but we do know the limit is there... but the lowly Atom CPU can support more memory?

                    Comment

                    • #11
                      Re: Why do z97 boards max out at 8GB per stick?

                      Yes, well, I wasn't getting anywhere there... In any event the anandtech article linked later in the thread is perhaps the most informative summary as oblique as it is ("unfixable issue") that seems to lay the blame squarely at the CPU's feet.


                      Sent from my iPhone using Tapatalk

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                      • #12
                        Re: Why do z97 boards max out at 8GB per stick?

                        Yes, a few more posts in the AF thread since I last posted. All I did was show the Intel memory specs from the Haswell processor datasheet, beyond that I don't have any other knowledge about the situation.

                        The Anandtech article about 16GB DIMMs is interesting and contains useful information IMO: AnandTech | I'M Intelligent Memory to release 16GB Unregistered DDR3 Modules

                        You can find 16GB DDR3 unregistered DIMMs now, but they are rare. They don't seem to be limited by current DRAM chip technology, since it seems current 8GB DIMMs are not using the 8 Gigabit memory chips. The article claims that most Intel CPUs (memory controller in the CPU) can't work with 8 Gigabit chips. That means the Intel specs are false about 8 Gigabit chips. It also states that AMD platforms which can support 64GB of DRAM can use 16GB DIMMs, so the claimed limitation of the Intel memory controller seems to be true.

                        Bottom line, any fix for this is out of our hands.

                        Comment

                        • #13
                          Re: Why do z97 boards max out at 8GB per stick?

                          !

                          TinkerTry IT @ home | Haswell Z97 limited to 32GB memory max, an unfortunate reality for virtualization enthusiasts
                          #1 - Please, when seeking help, enter the make and model of ALL parts that your system is comprised of in your Signature, or at least the model #'s in your System Specs, then "Save' it.
                          ____If you are overclocking, underclocking, or undervolting any parts, informing us of this and their values would prove beneficial in helping you.


                          #2 - Consider your PSU to be the foundation from which all else is built upon. Anything built upon a weak foundation is poorly built.

                          Comment

                          • #14
                            Re: Why do z97 boards max out at 8GB per stick?

                            That's kinda a strange article, particularly the quote from the Intel employee (supposedly), one part in particular:

                            "all the CPUs we have that presently support 64MB are all Ivy Bridge and below (the High End processors)."

                            Two points about this quote, the 32GB limit has been in place since the Mainstream Sandy Bridge generation of processors were introduced in early 2011. Before that, the triple channel Nehalem/i7-900 series processors had a 24GB memory limit. The socket 1156 Lynnfield processors had a limit of 16GB, and the earlier Core 2 processor platforms were limited to 16GB or less, depending on the chipset.

                            The difference to be noted here is the use of High End processors in the above quote, while all current Haswell processors including Devils Canyon and Z97 mother boards are considered Mainstream products by Intel. All the 'Z' boards and their processors back to and including Sandy Bridge are Mainstream products.

                            High End processors are denoted with an 'E' in their generation name, Sandy Bridge E, and Ivy Bridge E for example. They support 64GB of memory and can only be used with X79 chipset boards.

                            Intel's usual timetable for the release of a new CPU generation (like Haswell) starts with the Mainstream processors, and about a year later, the High End version of that processor generation is released. For example, a Mainstream Haswell i7-4770K was released in Q2 2013, and the High End Ivy Bridge E processors were released in Q3 2013. Mainstream Ivy Bridge processors were released in Q2 2012.

                            High End Haswell E processors do not exist yet, so of course "all the CPUs we have that presently support 64MB are all Ivy Bridge and below (the High End processors)", that's a given.

                            Intel Mainstream platforms since Sandy Bridge have always had the 32GB memory limit, for whatever reason. To find that surprising is surprising to me, particularly from an Intel employee.

                            Intel has been trying to get more enthusiasts (gamers?) into their High End processors and chipsets by giving them more memory capacity and more PCIe lanes (40 vs 16 on Mainstream), but most of them don't go for it.

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                            • #15
                              Re: Why do z97 boards max out at 8GB per stick?

                              Well for instance my Z77 Pro3 has a BIOS bug which would never allow 8Gb DIMMs (16GiB), of course the bug would not be noticed unless using the higher density DIMM's. It's easily fixed with a mod but without real 16GB DIMM's I can not confirm proper working only modify one of the 4GB DIMM's SPD so the BIOS sees it as a higher capacity DIMM. In this example a 16Gb DIMM (32GiB).

                              Click image for larger version Name: 32Gb.jpg Views: 1 Size: 62.6 KB ID: 754499

                              Of course IVB / SNB desktop CPU's only support 36-bit addressing so you will always be limited to less than 64GiB unlike Haswell which has 39-bit addressing (512GiB).

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