Power Consumption and TDP

The way AMD and Intel use the term Thermal Design Power (TDP) is different. Technically it is a measure of cooling ability needed for a given processor, which is how AMD use it, or the more common way is a measure of power consumption, how Intel does it. The question becomes whether it means sustained power, or turbo power - most people assume it's the latter, but Intel use it for the former (sustained) power. We describe this in detail in our article here:

https://www.anandtech.com/show/13544/why-intel-processors-draw-more-power-than-expected-tdp-turbo

There is also the added factor of the luck of the draw - two processors that have the same name can potentially vary wildly in power consumption. Both AMD and Intel apply 'binning' rules, such that CPUs that hit a minimum grade are stamped as that processor model. This means that a processor can either only just pass the grade, or be a super perfect chip, but still be sold as the same. There is also the possibility that the company could downgrade a higher model and rebadge it to the lower model in order to adjust inventory. This is something to keep in mind when looking at power numbers.

Power Consumption

Power consumption was tested on the system while in a single MSI GTX 1080 GPU configuration with a wall meter connected to a power supply with ~75% efficiency > 50W, and 90%+ efficiency at 250W, suitable for both idle and multi-GPU loading. Our method of power reading actually bypasses the power management of the UEFI and the board to supply components with power under load, instead using the readings that the system is directly be told from the CPU for managing fan speeds, temperatures, current protection, etc. This way of reading the power has positives and negatives, but provides a sustainable CPU-only comparison value.

In our test, we use affinity masking to test from 0 to double the threads of the CPU while running the POV-Ray benchmark, and reporting the peak power from around ~20 seconds into the test when all threads are loaded. The 'Full Load' value takes the peak value out of all the affinity mark sub-tests. POV-Ray uses up to AVX2 instructions, which can draw more power than non-AVX code.

Power (Package), Full Load

As expected, the 2500X consumes more power than the 2300X, but both are beaten by almost 10W by the Core i3-8350K, and the Core i5-8600K sits in between the two AMD chips. Perhaps suprisingly, our Ryzen 5 2500X sample consumes more power at load than our Ryzen 5 2600 chip, which is rated at the same TDP. It would appear that the 65W TDP of our Ryzen 5 2500X is set too low, or we just have a bad chip that is applying a lot of voltage. The winners in power here are the Ryzen APUs.

Gaming: F1 2018 AMD Ryzen 5 2500X and Ryzen 3 2300X Conclusion
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  • Daeros - Monday, February 11, 2019 - link

    Your Intel bias is showing again, Ian. You've pitted a very nice selection of midrange processors from AMD against some very nice, almost double the price chips from Intel. If you're going to include the i5-8400 and i5-8600k, why not the R7 2600x or 2700? They're price-point competitors. But then, Intel wouldn't be at the top of the charts in almost any of the tests, would they? Reply
  • Ian Cutress - Monday, February 11, 2019 - link

    All the data is in Bench for those parts. I mention repeatedly (as I did in our buyer's guide) that Intel doesn't really have anything competitive from 8th/9th Gen in the $120-$200 range. I put some parts in that are at least offer thread parity, as explained on page one of this review, if you read that far. But then again, Intel's 8th gen chips are priced well above the usual price right now.

    Subsequently, your data bias is showing. It's not about being at the absolute top of the graph. It never has. It's about competing with what's around you and some context either side from major competitors. If you want to compare higher priced parts against higher priced parts, then there's either a benchmark database to look at, or the corresponding reviews for those chips.

    All quite apart from which, most of my analysis is comparing the AMD parts to other AMD parts because they're not sold at retail and where they would fit in if they did. That's one of the major points of this review.
    Reply
  • c4v3man - Monday, February 11, 2019 - link

    Is Anandtech trying to acquire an Intel i3-8100 processor for testing? This would seem to be a fairly natural comparison point to these processors at it's $117 customer pricing level. Granted you can approximate the results off the i3-8350K, and assume it's roughly 10% slower, but having actual numbers would be preferred over manual re-calculations. Reply
  • HStewart - Monday, February 11, 2019 - link

    What about i5-8400T - according to ARC it price at $179 which will be in price range you stated

    https://www.intel.com/content/www/us/en/products/p...

    Big difference is that it does not have Hyperthreading, been 6 cores without hyperthreading it could be serious competitor to Ryzen 5 2500X - it does have lesser max frequency than normal 8400
    Reply
  • Korguz - Tuesday, February 12, 2019 - link

    HStewart...
    that price.. could be an intel suggested price, or the tray price....
    Reply
  • HStewart - Tuesday, February 12, 2019 - link

    It is the price on Amazon, and selling out

    https://www.amazon.com/Intel-CM8068403358913-Core-...
    Reply
  • MattMe - Tuesday, February 12, 2019 - link

    @Ian - Whilst not quite as militant as some other forum users, I do agree that the testing and comparisons you have used here are not the most appropriate or useful. A similarly priced Intel CPU like the i3 would demonstrate competitive value in the marketplace. If we are including the more expensive Intel CPUs (because of their similar thread count, which I understand) then the graphs should have the equivalently priced AMD alternatives, again to help consumers understand the value proposition from both sides.

    Regarding the games/GPU options, I feel the testing you have carried out is useful, and although it's unlikely these CPUs would be paired with such a high-end GPU, we are at least ruling out the GPU being the limiting factor until reaching 4k, where your graphs demonstrate that the CPU is no longer the bottleneck. Without doubling the number of tests and data presented in the articles, I feel you've presented the most useful benchmarks and information. You'll never please everyone, I suppose.

    Overall I think this is another fantastic write-up and appreciate the effort you put into the research and testing, but I can understand some people's frustrations when it comes to the comparisons you have chosen to demonstrate.
    Reply
  • mikato - Thursday, April 4, 2019 - link

    Well said
    "If we are including the more expensive Intel CPUs (because of their similar thread count, which I understand) then the graphs should have the equivalently priced AMD alternatives, again to help consumers understand the value proposition from both sides."
    Reply
  • Phynaz - Monday, February 11, 2019 - link

    Typical AMD - Hot and Slow Reply
  • formulaLS - Monday, February 11, 2019 - link

    Typical Phynaz, quit the forums and said he won't be coming back and ended up flat out lying about it. Grow up dude. Reply

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