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Thread: Current sharing on mb and gpu

  1. #11
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    Quote Originally Posted by jonnyGURU View Post
    Yep. Difference between a GTX 1080 and GTX 1080 mobile. Mobile has fewer transistor, smaller die, lower base core clock (although higher boost), slower memory, lower fillrate, less memory, lower processing power and lower TDP (150W vs. 250W).
    According to https://www.techpowerup.com/gpudb/ they are the same chip - same transistor count, die size, and memory clock; core clock is 50 lower on the non-mobile, and the TDP is 150W vs 180W. The memory size is the same 8GB too.

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    Just because they "dropped the M" doesn't mean it's the same chip.

    There's "GTX 1080" and "GTX 1080 for Notebooks".

    GeForce 10 (10xx) series for notebooks

    The biggest highlight to this line of notebook GPUs is the implementation of configured specifications close to (for the GTX 1060-1080) and exceeding (for the GTX1050/1050Ti) that of their desktop counterparts, as opposed to having "cut-down" specifications in previous generations. As a result, the "M" suffix is completely removed from the model's naming schemes, denoting these notebook GPUs to possess similar performance to those made for desktop PCs, including the ability to overclock their core frequencies by the user, something not possible with previous generations of notebook GPUs. This was made possible having lower TDP ratings as compared to their desktop equivalents, making these desktop-level GPUs thermally feasible to be implemented into a notebook chassis with better thermal dissipation solutions.
    http://www.notebookcheck.net/NVIDIA-....171212.0.html

    http://www.notebookcheck.net/NVIDIA-....178631.0.html

  3. #13
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    Quote Originally Posted by jonnyGURU View Post
    Just because they "dropped the M" doesn't mean it's the same chip.
    No it doesn't, but it still is.
    There's "GTX 1080" and "GTX 1080 for Notebooks".
    Yes because the GTX 1080 for notebooks has a MXM slot and the one for desktops has a PCI Express slot. The differences are in the PCB, power consumption and clock speed. But the GPU chip itself and the memory is just the same, like we already said.

    There aren't any differences in the GPU itself like fewer transistors or different specs like you said. The only specs that have changed are because the frequency/power consumption and PCB.

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    Quote Originally Posted by jonnyGURU View Post
    Nope, you seeing things that aren't there.

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    You're right. I was comparing the TI to the non-TI.

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    Video cards usually have multiple dc-dc converters (VRMs) to power various parts of the video card : one for ram (one major and one auxiliary/minor for gddr5) , one for gpu core, one for gpu auxiliary , and there's a couple more voltages typically required by video cards in order to work for which they use either dc-dc converters or linear regulators (5v for hdmi output, 1.8v for bios and some small things on nvidia cards, 0.9v for some internal gpu stuff)

    The easiest power splitting would be to power the memory directly from the motherboard (gddr5 needs something like 20-30w for 4GB and up to around 45-50w for 8GB if i'm not mistaken, both values well within the 60-75w budget). There's even some room for overclocking the chips.

    The DC-DC circuit (VRM as in voltage regulator module) uses multiple phases, it's not uncommon to have 6 or 8 phases on more powerful video cards. Typically, you have a DC-DC controller chip which sends pulses to each phase of the circit letting energy flow through each phase to the output.

    The DC-DC controller monitors the output voltage and keeps it as steady as possible no matter the amount of current used in tiny amounts of time by the device connected to the output (gpu core , memory chips etc).
    This is done by continuously adjusting the duty cycle for each phase, the number of pulses each second and the duration of on time versus off time for each pulse. So some phases can be connected to have the input 12v from the pci-e connectors, and some phases can be connected to the 12v from the pci-e motherboard slot.

    From memory, I think that in the case of reference RX 480 cards, the memory chips were powered from the slot, along with 2 or 3 out of the 6-8 phases for the gpu core.
    So out of the total 160w or something like that, about 120w were used by the gpu core, so about 40% of that were taken from the slot, or about 40-50w ... but 40-50w + those 30w or so for memory made the cards pull more than the allowed 75w value and that's why there was all that hoopla about not respecting the standards and all that crap.

    AMD fixed that through drives by re-programing the gpu dc-dc controller to increase the duty cycle of the phases connected to the extra pci-e connectors and reducing the duty cycle of the ones connected to motherboard slot.. basically making the card pull more power from the extra power connectors.

    If you (or anyone) is curious about layout of video cards, this guy has some relatively good videos on his youtube channel: https://www.youtube.com/playlist?lis...CMLuav8vjxqvmA

    He sometimes gets things wrong, but most of the time he's right.

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