Power Consumption

On AMD’s official specifications for the Ryzen 9 6900HS, it lists the TDP as 35 W: the same specifications as the 6900HX, but at an optimized TDP. The HS means that it can only be used in AMD-approved and codesigned systems that can get the best out of the unit: i.e. it is an ultraportable premium device. That being said, laptop vendors can customize the actual final power limit as high as 80W, with the idea that because they are using an optimized voltage/frequency binned processor, the laptop design that can dissipate that much can extract more sustained performance from the processor, this usually translates into a higher all-core frequency.

For our ASUS Zephryus G14, the standard default power profile, known as ‘Performance’, is meant to conform to AMD’s Power Management Framework, i.e. scale from Energy Saving to Performance as required. In this mode, the system has a sustained 45 W power draw.

Performance: 45W

Loading up a render like POV-Ray, the system spikes the CPU package power to 83 W and 80ºC, before very quickly coming down to 45 W and a slowly rising temperature to equilibrium at 87ºC.

With something a bit more memory heavy, such as yCruncher, the same power profile is shown, this time with the power around about 81ºC for most of the test because it spends more time on memory access than raw throughput.

For a real-world scenario, Agisoft also spikes up very high initially, before reaching a plateau at 45 W and 90ºC.

Turbo: 65W

The other option on offer for this system is the ‘Turbo’ Mode, which jacks everything up to 65 W sustained.

This means we hit the peak temperature limits quite quickly, and the system ramps down over time to the 65 W average power.

The yCruncher profile is a bit more varied due to the CPU performance going further while the memory performance staying the same, but we still see temperatures in the mid 90s and power hovering more around 75 W.

Agisoft’s Turbo profile is all about being temperature limited in this case, and we still end up in the sustained parts of the test around that 65 W value.

If we were to look at how the power was distributed in each mode:

In performance mode, we see 16.0 watts when one core is loaded, going down to 5.2 watts per core when all cores are loaded and a frequency of 3775 MHz.

Compare that to the Turbo Mode:

The single-core data is the same, nothing changes there, but we’re now up to 7.2 watts per core when fully loaded, and a much higher frequency at 4050 MHz. But this means we’re using 17 watts more power (or 38% more power) for only 275 MHz (a 7% gain).

Looking at the frequencies in this format, you can see a slight difference in performance, but seemingly not that much to justify the power difference. Then again, I suspect Turbo is only really for when you are fully charged and plugged into mains power anyway.

For the following benchmarks, we’re going to be using both Performance and Turbo modes, but also I put the CPU in a 35W power mode. As the 1 core and 2 core loading is below this, it shouldn’t affect the single-core performance that much, but it might give us an understanding of where it compares to previous generations.

Core-to-Core, Cache Latency, Ramp Performance Per Watt
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  • yankeeDDL - Tuesday, March 1, 2022 - link

    Great article, as usual.
    It seems clear that Intel's AL still has the performance advantage, however, in the Conclusion page, the performance comparison is reference to the nominal consumption (35W, 45W, 65W), while we know that Intel's part can reach twice as much power, in practice, making an apples-to-apples comparison quite difficult, especially in light of Intel's better scaling with more Power.

    Is there a way to check the exact performance per core under the same exact consumption (or scaled)?
    I am especially interested as a user of the 1165G, which is an absolute battery eater (and/or heater): it seems that AL is a huge improvement, but if it also draws 100W (instead of 45W) to beat Ryzen by a 10%, then it's not worth it. In my opinion.
    Reply
  • Spunjji - Tuesday, March 1, 2022 - link

    Yes, the overall picture that has built up is of Intel's Alder Lake winning out at higher power levels (40W+) while AMD coming out ahead below that.

    This is good, because it means that we have great options for people who want the best possible performance in a mobile form-factor and for people who want a more even balance of performance and power usage. It's a nicer situation to be in than when Intel complete owned the mobile segment, followed by the years of stagnation at 14nm.
    Reply
  • yankeeDDL - Tuesday, March 1, 2022 - link

    Agree on all points.
    Intel's Tiger Lake is an absolute disaster, and it is actually surprising that Intel only managed to lose 50% market share with such a lousy product compared to Ryzen.
    And equally surprising is the insane jump in performance and perf/watt achieved with AL. Definitely good for the consumers.
    Reply
  • mode_13h - Tuesday, March 1, 2022 - link

    > Intel's Tiger Lake is an absolute disaster

    That seems like an overstatement. It just didn't improve enough against Ryzen, particularly in light of the 5000-series' gains. However, especially in light of Ice Lake's disappointments, Tiger Lake didn't seem so bad.
    Reply
  • Alistair - Tuesday, March 1, 2022 - link

    Tiger Lake was a stroke of luck for Intel, their worst product ever during a massive silicon shortage. They spent the year selling quad cores because AMD was selling everything they could make, not because Tiger Lake was any good. Reply
  • bigboxes - Wednesday, March 2, 2022 - link

    For sure. I went with AMD for the first time since 2006 this last year. Reply
  • Samus - Thursday, March 3, 2022 - link

    The irony here is AMD mobile CPU's are widespread in lots of desktops and AIO's, even high end units. You would rarely, if ever, see Intel U-series parts in desktops\AIO's outside of USFF's or low-end AIO's with Celeron\Pentiums.

    This is happening partially because AMD doesn't have a wide product stack like Intel. And they don't need too. The AMD U-series parts are absolute performance monsters and have been for the last 3 generations.
    Reply
  • abufrejoval - Friday, March 4, 2022 - link

    I own both, a Ryzen 5800U in a notebook and an i7-1165G7 as a NUC.

    They are really quite comparable, both in iGPU performance, in scalar CPU power and even in multi-threaded CPU power.

    At 15 Watts the 8 Ryzen cores operate below the CMOS knee, which means they have to clock so low they can't really gain much against 4 Tiger Lake cores clocking above it. Synthetic benchmarks may prove a lead that's next to impossible to realize or really relevant in day-to-day work. For the heavy lifting, I use a 5950X, which isn't that much faster on scalar loads, but runs almost as many rings around the 5800U as the i7-1165G7: the extra Watts make more of a difference than the cores alone.

    My impression is that the Ryzen needs the higher power envelope, 35 or even 65 Watts, and of course a matching workload to put those extra cores to work. AMD's primary aim for their APUs was to cover as many use cases as possible from a single part and they do amazingly well. If they could afford to do a native 4 core variant as well, I'm pretty sure that would outsell the 8 core.

    In fact the SteamDeck SoC would probably make a better notebook part for many (not everyone).

    And there is nothing wrong with Tiger Lake, except that perhaps today there are better SoCs around: it was and remains a welcome improvement over the previous generations from Intel.

    Buy it used and/or cheaper than these AL parts and you should have little to complain about... unless complaining is what you really enjoy.
    Reply
  • mode_13h - Tuesday, March 1, 2022 - link

    > Great article, as usual.

    I thought so, as well, which was a relief. Then, I noticed the by-line:

    "by Dr. Ian Cutress"
    Reply
  • lemurbutton - Tuesday, March 1, 2022 - link

    People shouldn't care that much about AMD and Intel on laptops right now. M1 series completely destroys both. AMD and Intel are 3-4 years behind. Reply

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