Power Consumption: TDP Doesn't Matter

Regular readers may have come across a recent article I wrote about the state of power consumption and the magic 'TDP' numbers that Intel writes on the side of its processors. In that piece, I wrote that the single number is often both misleading and irrelevant, especially for the new Core i9 parts sitting at the top of Intel's offerings. These parts, labeled 95W, can go beyond 160W easily, and motherboard manufacturers don't adhere to Intel official specifications on turbo time. Users without appropriate cooling could hit thermal saving performance states very quickly.

Well, I'm here to tell you that the TDP numbers for the G5400 and 200GE are similarly misleading and irrelevant, but in the opposite direction.

On the official specification lists, the Athlon 200GE is rated at 35W - all of AMD's GE processors are rated at this value. The Pentium G5400 situation is a bit more complex, as it offers two values: 54W or 58W, depending on if the processor has come from a dual-core design (54W) or a cut down quad-core design (58W). There's no real way to tell which one you have without taking the heatspreader off and seeing how big the silicon is.

For our power tests, we probe the internal power registers during a heavy load (in this case, POV-Ray), and see what numbers spit out. Both Intel and AMD have been fairly good in recent memory in keeping these registers open, showing package, core, and other power values. TDP relates to the full CPU package, so here's what we see with a full load on both chips:

Power (Package), Full Load

That was fairly anticlimactic. Both CPUs have power consumption numbers well below the rated number on the box - AMD at about half, and Intel below half. So when I said those numbers were misleading and irrelevant, this is what I mean.

Truth be told, we can look at this analytically. AMD's big chips have eight cores with hyperthreading have a box number of 105W and a tested result of 117W. That's at high frequency (4.3 GHz) and all cores, so if we cut that down to two cores at the same frequency, we get 29W, which is already under the 200GE TDP. Scale the frequency back, as well as the voltage, and remember that it's a non-linear relationship, and it's quite clear to see where the 18W peak power of the 200GE comes from. The Intel chip is similar.

So why even rate it that high?

Several reasons. Firstly, vendors will argue that TDP is a measure of cooling capacity, not power (technically true), and so getting a 35W or 54W cooler is overkill for these chips, helping keep them cool and viable for longer (as they might already be rejected silicon). Riding close to the actual power consumption might give motherboard vendors more reasons to cheap out on power delivery on the cheapest products too. Then there's the argument that some chips, the ones that barely make the grade, might actually hit that power value at load, so they have to cover all scenarios. There's also perhaps a bit of market expectation: if you say it's an 18W processor, people might not take it seriously.

It all barely makes little sense but there we are. This is why we test.

Gaming: F1 2018 Overclocking on AMD Athlon 200GE
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  • brakdoo - Monday, January 14, 2019 - link

    The reason why I bought the 200GE last month: The 5400 is 75€+ and was above 80 when I bought my parts in my country. The Intel shortage makes it easy to decide but I that it'll be over soon.

    BTW: Does graphics performance have an influence on WebGL stuff like google maps or isn't that challenging enough?
    Reply
  • blu42 - Monday, January 14, 2019 - link

    Shouldn't 'measured under heavy load' suggest a heavy load for the entire package, not the CPU cores alone? Reply
  • Robotire - Monday, January 14, 2019 - link

    This. I’m surprised a pure CPU (I think?) load was used. I would be interesting to know power usage while gaming.

    Also I’m more likely to buy a component that uses less power… but I guess some SUV owners might prefer it the other way.

    Otherwise it’s a very interesting article, thanks! I don’t care at all about overpriced products, but reviews like this one are useful.
    Reply
  • SaturnusDK - Monday, January 14, 2019 - link

    It's important to note that even if you could get a G5400 at the $64 MSRP, it would be 16% more expensive than the $55 Athlon. However, you can't get the G5400 for $64. The lowest price I have ever seen it retail at is $80 which makes the choice for a absolutely bottom bin bargain buyer easy.
    If you're still even contemplating the G5400 at it's actual $80 price tag then it would be wise to consider if you can go the extra $20 and get the vastly superior 2200G instead.
    Reply
  • Drumsticks - Monday, January 14, 2019 - link

    As of right now, the Pentium G5400 is $129.99 on Newegg (??????) and $101 on Amazon from an alternate seller. OTOH, the Athlon 200GE is readily available from both for $60. That's a pretty stark difference. Reply
  • ikjadoon - Monday, January 14, 2019 - link

    The pricing is out of whack at Newegg: G5400 for $129, G5500 (3.8GHz w/ UHD630) for $114, and G5600 (3.9GHz w/ UDH630) for $113.

    You save $16...while buying a higher-end part.

    B&H Photo has it for slightly-less absurd 24% markup over MSRP ($80): https://www.bhphotovideo.com/c/product/1393125-REG...
    Reply
  • khanikun - Tuesday, January 15, 2019 - link

    Ya, the G5400 makes no sense with it's pricing. An i3 8100 is a quad core 3.6 ghz proc with UHD630 for $119. Unless power usage is a main concern, I wouldn't bother with any of those G procs currently. Until prices drops, doesn't make much sense to buy them. Reply
  • Zim - Saturday, January 19, 2019 - link

    $65 at Fry's https://www.frys.com/product/9499961 Reply
  • StevoLincolnite - Tuesday, January 15, 2019 - link

    Even in Australia... The G5400 is $129. - Doesn't make sense to grab that when you can get the Ryzen 3 2200G for $155... You could probably find a motherboard that reduces that $26 pricing gap.

    Otherwise the 200GE is $79... $50 cheaper.

    The G4920 is more inline with the 200GE's price at $89 currently... And at that point, the 200GE is still the decided victor.
    Reply
  • PVG - Monday, January 14, 2019 - link

    I think TDP has to cover simultaneous heavy usage of both the CPU and IGP. POV-Ray only really stresses the CPU side.
    I see how one can disregard the IGP contribution on higher end chips, but on models like this, where there's a big chance the IGP will actually be put to use, I fell it should be taken into account, on the power measuring front.
    Reply

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