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Corsair 2 x 24GB DDR5-7000 Memory Linux Performance

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  • #11
    6000 isn't the max, it's just the recommended RAM speed based on AMD's findings about price/performance. Per various benchmarking sites like Tom's Hardware https://www.tomshardware.com/reviews...000-c34-review 6400-6600 is as far as you can really go though, so yeah 7000 MHz RAM is useless in a Zen 4.

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    • #12
      Originally posted by Luke_Wolf View Post
      6000 isn't the max, it's just the recommended RAM speed based on AMD's findings about price/performance. Per various benchmarking sites like Tom's Hardware https://www.tomshardware.com/reviews...000-c34-review 6400-6600 is as far as you can really go though, so yeah 7000 MHz RAM is useless in a Zen 4.
      And interestingly Zen 4 only officially supports DDR5-5200, even though (IIRC) they recommend DDR5-6000 in marketing materials or through a representative.

      We could see much higher speeds supported with Zen 5, e.g. DDR5-7200 to DDR5-8000.

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      • #13
        Originally posted by Luke_Wolf View Post
        6000 isn't the max, it's just the recommended RAM speed based on AMD's findings about price/performance. Per various benchmarking sites like Tom's Hardware https://www.tomshardware.com/reviews...000-c34-review 6400-6600 is as far as you can really go though, so yeah 7000 MHz RAM is useless in a Zen 4.
        Actually, it's pretty much the top that you can count on. Almost everything above that is a lottery.
        Article that you mention talks about _their_ chip and other "good samples".

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        • #14
          I haven't been following the latest developments in PC hardware as closely as I once did. But I'm used to memory modules always having a capacity that is a whole power of 2. So after 16GB modules, I thought we'd go straight to 32GB modules. 24GB modules, that just feels weird.

          Maybe I'm just being autistic about it, I don't know. How long has this been a thing?

          UPDATE: I searched a bit on-line for the answer, and apparently, this is allowed by the DDR5 specification, and the "whole power of two" thing was more of a traditional convention in the PC industry, with other hardware such as smartphones already having done away with it for some time. (Indeed, some phones even shipped with 3GB of RAM, which is not only not a whole power of 2, but an odd number, which feels even dirtier. ) Source: https://www.anandtech.com/show/17117...b-ddr5-modules
          Last edited by SteamPunker; 22 April 2023, 09:50 AM.

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          • #15
            Originally posted by avis View Post
            Desktop Zen 4 CPUs don't support/run with DDR5 faster than 6000MHz. Just so you knew. And if you have four DIMM slots populated you're f*cked: only 3600MHz for you.
            Strangely mobile APUs support up to LPDDR5x-7500.
            what you really want is this:
            " AMD and JEDEC Develop DDR5 MRDIMMs With Speeds Up To 17,600 MT/s"
            Phantom circuit Sequence Reducer Dyslexia

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            • #16
              Originally posted by Brane215 View Post

              Actually, it's pretty much the top that you can count on. Almost everything above that is a lottery.
              Article that you mention talks about _their_ chip and other "good samples".
              and people also forget infinity fabric is tied to dram speed as well. so its always in a 1:1 ratio. that means memory is also limited by infinity fabric. you can decouple it but you'll get a pretty big performance hit. 6000mhz is pretty much the max because of infinity fabric. buildzoid of actual hardcore overclocking was able to get higher speeds by decoupling but the performance loss isn't worth it. the memory controller on the i/o die still doesn't allow for speeds high enough to make up for the performance loss. and even with zen4 chips that can do 6200-6400, many of them are not fully stable. random crashes / system freezes can happen out of the blue. zen4 really isn't stable above 6000.

              intel on the other hand as noted by michaels own review can do 7000 fairly easily with single rank kits. others have hit 8000 but most wont. and intel's, like zen4, really gets bad when dealing with four modules to occupy all four dim slots. or dual rank, high capacity kits. 6000mhz single rank 32gb kits will work fine. but dual rank 64gb kits? even if its just two 32gb modules, at dual rank per module its really stressful on the controller. with my 13700kf i went with a 5200mhz kit because it was one of the very few 64gb kits on my motherboards QVL for 64gb and i didn't want to deal with any headaches.
              Last edited by pieman; 22 April 2023, 09:11 PM.

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              • #17
                Originally posted by pieman View Post
                and people also forget infinity fabric is tied to dram speed as well. so its always in a 1:1 ratio. that means memory is also limited by infinity fabric. you can decouple it but you'll get a pretty big performance hit. 6000mhz is pretty much the max because of infinity fabric. buildzoid of actual hardcore overclocking was able to get higher speeds by decoupling but the performance loss isn't worth it. the memory controller on the i/o die still doesn't allow for speeds high enough to make up for the performance loss. and even with zen4 chips that can do 6200-6400, many of them are not fully stable. random crashes / system freezes can happen out of the blue. zen4 really isn't stable above 6000.

                intel on the other hand as noted by michaels own review can do 7000 fairly easily with single rank kits. others have hit 8000 but most wont. and intel's, like zen4, really gets bad when dealing with four modules to occupy all four dim slots. or dual rank, high capacity kits. 6000mhz single rank 32gb kits will work fine. but dual rank 64gb kits? even if its just two 32gb modules, at dual rank per module its really stressful on the controller. with my 13700kf i went with a 5200mhz kit because it was one of the very few 64gb kits on my motherboards QVL for 64gb and i didn't want to deal with any headaches.
                It is a bit more complicated. But generally speaking dual rank shouldn't affect that much max speeds comparing to single rank. Problem is driving 4 seperate traces for 4 seperate sticks is what really hurts signal integrity and prevents sensible overclocking. Also IF isn't always die to DRAM speed, it is tied up to certain max frequency and if you cross it, it becomes decoupled and hurts performance/latency. IF on zen 4 clocks max to 3GHz, what considering we use double rate RAM means max 6000MHz on ddr5 kits so even if you could go beyond 6000MHz it would hurt you not help you.

                Motherboard manufacturers should really make more motherboards for ddr5 that have 2 slots, 2 slots means shorter traces, less traces, lower costs and better singnal integrity. Heck possibly it could even allow to have less layers in motherboard and that would even more bring costs down.

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                • #18
                  Originally posted by avis View Post
                  Strangely mobile APUs support up to LPDDR5x-7500.
                  Nothing strange about it. DDR on desktop has 2 sockets in path. LPDDR on mobile has 0.

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                  • #19
                    Originally posted by piotrj3 View Post
                    Motherboard manufacturers should really make more motherboards for ddr5 that have 2 slots, 2 slots means shorter traces, less traces, lower costs and better singnal integrity. Heck possibly it could even allow to have less layers in motherboard and that would even more bring costs down.
                    ASRock's cheapest B650 is exactly that.

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                    • #20
                      Originally posted by SteamPunker View Post
                      UPDATE: I searched a bit on-line for the answer, and apparently, this is allowed by the DDR5 specification, and the "whole power of two" thing was more of a traditional convention in the PC industry, with other hardware such as smartphones already having done away with it for some time. (Indeed, some phones even shipped with 3GB of RAM, which is not only not a whole power of 2, but an odd number, which feels even dirtier. ) Source: https://www.anandtech.com/show/17117...b-ddr5-modules
                      It sounds like you're confusing total system memory with module size. Total system memory has never been tied to power-of-two, with "odd" sizes actually quite common place. 3 GB of RAM is nothing new, and not limited to phones. Most all the intel products from around 12 years ago had triple-channel memory, so total system RAM of 3 GB or 6 GB or 12 GB was the norm. At the time, it was only AMD systems that had 2 or 4 or 8 GB of memory. Having three sticks of memory was common in the Super Socket-7 days as well, with 384 MB, 768 MB and 1.5 GB being common memory sizes. All of these "odd" sums however were composed of base-two modules. e.g. 3x1G=3G. 3x512M=1.5G. and so forth.

                      What is unique here in the DDR5 era as highlighted by this article, is the advent of non-base-two sized modules. This is unrelated to total system memory size, phones with 3GB are not relevant to this discussion. Does that make sense?
                      Last edited by torsionbar28; 24 April 2023, 12:29 AM.

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