Questions about DDR DPC and ranks, speed & CAS Latency for PC upgrade

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  1. Posts : 425
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       #1

    Questions about DDR DPC and ranks, speed & CAS Latency for PC upgrade


    Sorry for the long post. Lots of questions

    I'm getting closer to upgrading my X299 system. Or is that downgrading? I've always needed more PCIe lanes than mainstream motherboards/CPU's have offered, but it seems I'm just going to have to make some sacrifices.

    I'm either going to get a Z790 motherboard that has at an x4 PCIe slot off the chipset to I can add extra USB 3.0 ports if the board has 10G LAN (Eg ASUS Proart), or add a 10G NIC if it has 2xUSB 3.0 headers. My whole home is 10G wired.

    Gigabyte is out, as you can only get 5.1 audio by running cables to the front of your PC.
    Other boards say the only way to get "spatial" audio is to use the front ports. I don't like the idea of having to run extension cables to the front of my PC for audio. btw: I never use headphones, a microphone or a webcam. I'm not sure if spatial audio is even an issue?

    I'm struggling with the whole DDR5 scenario.
    The ASUS Z790 Apex only has two memory slots. If I fill that I have 1DPC, right?

    On boards with 4 slots, I plan on only using 2 slots as the deficit for 4 sticks from reviews I read seems to be about 9%-10%,
    So 2 sticks on a 4 slot motherboard is 1DPC?

    So it seems I'm looking for Single sided sticks. That is 1R. So A single sided kit of two sticks is 1DPC 1R. Is my understanding correct?

    Finding 32GB 1R kits locally has been all but impossible so far. I may have to settle for a 24GB 1R kit

    I've been saving for some time. My primary criteria is "Best possible performance". Price is only a factor because here in Australia there is a very limited selection and prices can be as high as 3 times the USD price.

    With timings, they are all over the place. Am I better off buying memory with the CL less than or equal to half the memory frequency (I read somewhere it is relevant. Eg a 6000mhz kit would not have a CL higher than 30). Should I look for memory where all of the timings are as close as possible to each other? Or is CL still the most relevant factor?

    It seems PCIe x5 is all hype at the moment. I guess better options will arrive over time. You either have a SSD running PCIe x5 and lose 50% of your GPU bandwidth or run your GPU at 100% bandwidth and lose your PCIe x5 SSD. I've yet to find a motherboard that lets me have my cake and eat it too :)

    So if my GPU is PCIe x4 and I lose 50% of its bandwidth (coz it's now running at x8 with a SSD), that means it's effectively running at PCIe x3 at 100%? For video editing, rendering, game design, and gaming will this be an issue, say withing the next 2-3 years?

    I'm looking at boards like;
    ASUS Z790 Proart
    ASUS Z790 ROG Maximus Apex
    ASUS Z790 ROG Maximus Hero
    MSI MEG Z790 Ace.

    I will run at least 4 PCIe x4 SSDs (probably Kingston KC3000D 2tb), preferably with 64GB DDR5. 10G LAN wired. No wireless. a 10TB Spinner and an RTX 3080 Ti GPU. 2x 32" 4K HDR monitors and a 1200W PSU with a 360mm cooler running push-pull. The CPU will be a 13700K (No point spending an extra A$200+ for a 2% performance uplift, especially with power consumption and heat). I will be adjusting the Long duration and short duration power limits, or setting negative offsets to try to alleviate throttling, though this seems to mostly occur in synthetic workloads rather than real world, but in summer here the ambient temps can be as high at 40 Celsius.
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  2. Posts : 1,204
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  3. Posts : 425
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       #3

    This seems to be more about AMDs shortcomings than about Intel.
    But it doesn't answer my questions.
    Thanks for posting it though.
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  5. Posts : 425
    Windows 10
    Thread Starter
       #5

    Interesting read.
    Ok, so single sided kit of two sticks is 1DPC 1R.
    So I'm looking for a 2x32GB Single sided kit. Right. Don't believe I've ever seen on on a QVL or on an Australian retailers website, but I could have missed something. The QVLs I've seen do list one or two 24GB kits, but I can't remember if they were SS or DS... I'll have to go back and look, but in any case, again I couldn't find a retailer selling any.

    So my remaining questions are about latency vs speeds and what's best.
    I understand latency is CL * 2000 divided by the frequency. 9.69 is about the best I've seen. IIRC it was a 6400mhz kit. But it was 1DPC 2R, and I'm looking for 1DPC 1R.

    But lets say 10ns just to round it off. If one kit has a 10ns latency with a frequency of 6400mhz and another kit has a 10ns latency with a 7600 mhz speed is it worth paying the extra to buy the 7600mhz kit?

    And... CL is only one of 4 timings on RAM. Should I look for memory with the other 3 as low as possible? Or, as is DDR4 days, is CL the only important timing? Surely the other have some interplay?

    The other question was about PCIe5 and the halving of the GPU's bandwidth and whether if I buy a PCIe 5 SSD it's not going to reduce performance enough to be noticeable, particularly on long rendering jobs.
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  6. Posts : 23,799
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       #6

    @Wobitancrawfodi


    And for the lazy folks... GSkill RAM Configurator...

    Fill in the three boxes and click on Search. Add further filters on the left side...
    RAM Configurator - G.SKILL International Enterprise Co., Ltd.

    They do a bit more testing than the motherboard manufacturers... so their results are a bit more, in depth.


    Generally, a two stick set (dual channel board), will give the best results.
    So if you want 64GB of RAM, get a 2x 32GB set.
    For a triple channel board, look for a three stick set, etc.


    Corsair has a Memory Finder tool, that works fine for older boards.
    They're a bit slow updating for the newer boards.
    Corsair also aims more for absolute stability, so they don't set their timings as fast as some other companies.


    Interesting RAM guide...
    RAM explained: Why two modules are better than four / single vs. dual-rank / stability testing | MSI Global English Forum
    Last edited by Ghot; 26 Jul 2023 at 06:43.
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  7. Posts : 1,204
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    So here's what I would probably choose between. They also have the RGB version of these ones, but... for future upgrades I think you might want to save your smackeroonies. 🙃

    Corsair Vengeance 32GB (2x 16GB) DDR5 6400MHz C32 Memory - Black | AusPCMarket

    Corsair Vengeance 64GB (2x 32GB) DDR5 6400MHz C32 Memory - Black | AusPCMarket
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  8. Posts : 425
    Windows 10
    Thread Starter
       #8

    hdmi said:
    So here's what I would probably choose between. They also have the RGB version of these ones, but... for future upgrades I think you might want to save your smackeroonies. ��

    Corsair Vengeance 32GB (2x 16GB) DDR5 6400MHz C32 Memory - Black | AusPCMarket

    Corsair Vengeance 64GB (2x 32GB) DDR5 6400MHz C32 Memory - Black | AusPCMarket
    Thanks for that. The 64GB kit is 1DPC 2R, not what I was looking for but it seems I don't have much choice here.
    AusPCMarket is what we call a "grey marketer". Like Skycomp. They don't actually stock anything, the source it from other retailers when orders are placed. But that means there must be a retailer that does have it in stock if APM is saying they have it

    I could care less about RGB, so that's fine.

    In any case, this is not on the QVL for MSI, ASUS or ASRock. So it's a suck it an see if it works. If it doesn't I have to cover return shipping, and pay a 25% restocking fee. Hence why my preference is for local retailers. That way I only have to pay the 26% restocking fee.
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  9. Posts : 1,204
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       #9

    I think I probably found it:
    64GB DDR5 (2x32G) Corsair 6400MHz Vengeance CMK64GX5M2B6400C32 RAM | CA
    With the XMP 3.0 it should work at the rated clock frequency and timings on all of those Z790 motherboards that you listed, but what you can NOT do is buy two Dual Kits so as to combine them to get a total of four DIMMs and expect THAT to work at this same rated clock speed and timings. Dual Kit = "matched pair", handpicked by Corsair because enabling XMP in BIOS automatically means that your RAM will be overclocked to make it work at default overclock settings as defined by the XMP profile of the RAM in question. So, when overclocked in this manner these higher-clocked DIMMs rarely run stable if not all the DIMMs in your PC came bundled together by the DIMM manufacturer as part of one and the same Kit. Kit = sold as a single packet in original unopened, SEALED, packaging from the factory so as to avoid some vendors cheating on you. E.g., by switching various different DIMMs of the same exact make and model around in hopes of getting better than usual overclock results in their own PC before they sell all their other DIMMs─that also are of this same exact make and model─to unsuspecting victims only because they know that they can probably get away with it. Especially when there simply ARE no real, direct competitors to be found anywhere near the same area/region when it comes to these specific types of hardware components, anyway to begin with.
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  10. Posts : 425
    Windows 10
    Thread Starter
       #10

    Agreed.

    I think 64GB will be enough though. Two years ago 64GB was priced up around $900. The first F4-3600C16Q-32GTZN kit I bought cost me $549. Memory prices have come down a lot, even in Australia, so I'm going to get 64GB for less than I paid for my 32GB kit. Can't complain about that.

    I'm running that kit at 3733, so a latency of 8.5ns. I'm actually going to go backwards with the DDR5

    And, since I last posted I found a local retailer that sells one of the 6400mhz kit, but he was evasive on the "if it doesn't perform as described" question. Still, RAM manufacturers say they are compatible with 700 series boards. It's the motherboards makers that want to be picky.

    The MSI Z790 Apex, which is probably the board I'm going to buy as the ASUS is terribly vague on the RAM support and ASRock's Z790 Taichi flagship board will only run at 4000mhz. So, with the 1DPC 2R kit I should get the full 6400mhz out of it on the MSI board.

    Corsair 64GB (2x32GB) CMH64GX5M2B6400C32 Vengeance RGB C32 6400MHz DDR5 DRAM - Black - msy.com.au
    MSI MEG Z790 ACE LGA 1700 E-ATX DDR5 Motherboard - msy.com.au
    Intel Core i7 13700KF 16 Core LGA 1700 CPU Processor - msy.com.au

    Now, just need to know whether there is any value in pursuing a PCIe 5 SSD, regarding my question above on the GPU bandwidth. Although, they are predictably expensive, so maybe I will wait a while before I buy one. I plan on this being my last major upgrade for a few years, so I still would like to know if I do purchase a new SSD if the impact on my GPU will negative impact it's performance compared to what I have now.

    I have a couple of spare 10G PCIe NICs that I can plug into PCIe3 on the motherboard so that gives me 10G LAN speeds.

    Given the power draw and temps of the 13th CPUs I may also have to update my cooler, which is a bit suspect as to LGA 1700 compatibility anyway...

    Getting there :)
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