Comment on New Laptop Memory Is Here! LPCAMM2 Changes Everything! - iFixit Video

• bonus_crab@lemmy.world ⁨1⁩ ⁨month⁩ ago

  Yeah mega transfers. 1 transfer is 8 bytes. the DD in DDRX is double data so it can send 2 transfers per channel per clock. CPUs pretty much always use 2 channels, so the formula is just GBps = 32 * MT/s. My PC has 6000MT/s DDR5 in a dual channel config so thatd be 192GBps.

  Idk how apple is getting above 300GBps, maybe theyre counting the integrated GPU as part of the total. GPUs often have 4 or 6 or 8 channels so thatd make sense…

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  • victorz@lemmy.world ⁨1⁩ ⁨month⁩ ago

    Thank you for going into detail.

    Okay so, 1 T = 8 B. DD = 2 T/channel. And with 2 channels we get 4 T, so 4 × 8 = 32. Okay I get you. Thanks so much. 🙂

    Yeah that’s a crazy number with 300-500 GBps if DDR5 is doing around 200… Absolutely insane actually. But yeah, good theory about the GPU. Those bastards, padding the numbers.

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    • falkerie71@sh.itjust.works ⁨1⁩ ⁨month⁩ ago

      I don’t think its fair to call it “padding”. They’re on the same die anyways and share the same memory pool through the same connections, makes sense they all have the same speed. I imagine Intel/AMD CPUs with iGPUs also share memory speeds and are both limited to how many ram channels you have configured. Apple very much could achieve that kind of speed by having more ram channels. Have the ram working in quad-channel mode, and you double the 192 GBps to 384 GBps.

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      • victorz@lemmy.world ⁨1⁩ ⁨month⁩ ago

        Good points. I retract my name-calling!

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  • falkerie71@sh.itjust.works ⁨1⁩ ⁨month⁩ ago

    Anandtech has an article about the M3 and details about it’s memory speed. M3 has 100 GBps, M3 pro 150, and M3 max 400.

    So theoretically there’s no stopping laptop manufacturers to have multiple LPCAMM2 slots to achieve such speeds, correct?

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  • Blue_Morpho@lemmy.world ⁨1⁩ ⁨month⁩ ago

    Wiki says M3 uses on package unified memory, so the GPU channels are also the CPU channels.

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