5 ms·

The 3900X still uses ~140 W at full load with a 105 W TDP. And still just like Intel, if you limit the clock speeds you can make it use 105 W, 65 W, or 35 W at

The 3900X still uses ~140 W at full load with a 105 W TDP. And still just like Intel, if you limit the clock speeds you can make it use 105 W, 65 W, or 35 W at full load, just like with Intel chips. AMD calculates the TDP a bit differently, but nothing really changes fundamentally. All CPUs in a generation are essentially the same chip, TDP is completely irrelevant.

jankotek 7y ago
Not the same chip, quality differs, some units would require higher voltage for the same frequency. Some CPUs are more power efficient because they can take lover voltage.
- pingyong 7y ago
  Yeah and those chips are typically the ones being sold as higher TDP chips.
pizza234 7y ago
For users who have a fixed TDP budget, there's a substantial difference. The AMD power calculation is not "bit different", it's Intel who is cheating big time. On a system with constrained power values, those who buy Intel will suffer a substantially higher hit than those who buy AMD.
- pingyong 7y ago
  > For users who have a fixed TDP budget, there's a substantial difference. I really, really don't see how. Both TDPs have very little connection to how much power the chips actually pulls at full load. 105 to 140 isn't useful in any way. If it was 107, sure, but 140 is 1/3rd higher than "spec" (I write "spec" because TDP isn't supposed to tell you what the highest power draw possible is if your cooling can dissipate more than the TDP in the first place, people just somehow seem to use it that way). If you have a fixed TDP cooler, all you have to do is put that cooler on CPUs and see which ones will be faster. No looking at the specs required. If you have a fixed power consumption budget, but a better cooler, all you have to do is downclock until the CPU stays within that budget and then compare performance. Again, spec wasn't useful.
JamesMcMinn 7y ago
140W is considerably closer to the stated 105W TDP value of the 3900X than a "95W" 9900k which can easily pull down 180W. Whilst I agree that TDP shouldn't be taken as gospel, at least in AMDs case, it can be a useful approximation the amount of heat generated (and thus power draw). If you then compare the actual performance per watt, a 12 core CPU at 3.1 base / 4.2 boost pulling down approximately 65W is very impressive. Something similar from Intel (in terms of number of cores at even just the 3.1 base frequency) would likely have a TDP of at least 120W.
- pingyong 7y ago
  >140W is considerably closer Closer, yes, but more useful? Both are off by a mile - not to mention that TDP isn't supposed to tell you a chip's maximum power consumption in the first place. It's supposed to tell you how good your cooler has to be to sustain base clocks / single core turbo, or in AMD's case, to sustain base clocks and some? boost clocks for a limited time. >If you then compare the actual performance per watt Performance per watt can certainly be interesting for many people. Performance per watt just isn't connected to TDP. The 3900X (105 W TDP) has higher performance per watt than the 9900K (95 W TDP). Probably at any frequency - although potentially the 3900X can't clock down as much. The 9900K can run Cinebench without a cooler after all (at least the 8700K can, so I'd suspect the 9900K can do that too), while the AMD processors can't. Also, the 3900 (65 W TDP) has the same performance per watt as the 3900X (105 W TDP), if you let them run at the same clock speeds.
  - juergbi 7y ago
    Ryzen SKUs with a 105W TDP have a power limit (PPT) of 142W at stock. 65W TDP SKUs have a power limit of 88W. I.e., while these CPUs are allowed to use more power than their TDP, it's limited to 35% above the TDP. This means that the advertised TDP is not just an arbitrary number they slap on the package.
    - pingyong 7y ago
      It's not an arbitrary number on Intel's CPUs either, it's just still not very useful. Or at least it's not useful as an indicator of some sort of technological progress. If you limit a 3900X to 3900 clock speeds and voltages, it's going to behave exactly the same.

jankotek 7y ago

Not the same chip, quality differs, some units would require higher voltage for the same frequency. Some CPUs are more power efficient because they can take lover voltage.

pingyong 7y ago
Yeah and those chips are typically the ones being sold as higher TDP chips.

pizza234 7y ago

For users who have a fixed TDP budget, there's a substantial difference. The AMD power calculation is not "bit different", it's Intel who is cheating big time. On a system with constrained power values, those who buy Intel will suffer a substantially higher hit than those who buy AMD.

pingyong 7y ago
> For users who have a fixed TDP budget, there's a substantial difference. I really, really don't see how. Both TDPs have very little connection to how much power the chips actually pulls at full load. 105 to 140 isn't useful in any way. If it was 107, sure, but 140 is 1/3rd higher than "spec" (I write "spec" because TDP isn't supposed to tell you what the highest power draw possible is if your cooling can dissipate more than the TDP in the first place, people just somehow seem to use it that way). If you have a fixed TDP cooler, all you have to do is put that cooler on CPUs and see which ones will be faster. No looking at the specs required. If you have a fixed power consumption budget, but a better cooler, all you have to do is downclock until the CPU stays within that budget and then compare performance. Again, spec wasn't useful.

JamesMcMinn 7y ago

140W is considerably closer to the stated 105W TDP value of the 3900X than a "95W" 9900k which can easily pull down 180W. Whilst I agree that TDP shouldn't be taken as gospel, at least in AMDs case, it can be a useful approximation the amount of heat generated (and thus power draw). If you then compare the actual performance per watt, a 12 core CPU at 3.1 base / 4.2 boost pulling down approximately 65W is very impressive. Something similar from Intel (in terms of number of cores at even just the 3.1 base frequency) would likely have a TDP of at least 120W.

pingyong 7y ago
>140W is considerably closer Closer, yes, but more useful? Both are off by a mile - not to mention that TDP isn't supposed to tell you a chip's maximum power consumption in the first place. It's supposed to tell you how good your cooler has to be to sustain base clocks / single core turbo, or in AMD's case, to sustain base clocks and some? boost clocks for a limited time. >If you then compare the actual performance per watt Performance per watt can certainly be interesting for many people. Performance per watt just isn't connected to TDP. The 3900X (105 W TDP) has higher performance per watt than the 9900K (95 W TDP). Probably at any frequency - although potentially the 3900X can't clock down as much. The 9900K can run Cinebench without a cooler after all (at least the 8700K can, so I'd suspect the 9900K can do that too), while the AMD processors can't. Also, the 3900 (65 W TDP) has the same performance per watt as the 3900X (105 W TDP), if you let them run at the same clock speeds.
- juergbi 7y ago
  Ryzen SKUs with a 105W TDP have a power limit (PPT) of 142W at stock. 65W TDP SKUs have a power limit of 88W. I.e., while these CPUs are allowed to use more power than their TDP, it's limited to 35% above the TDP. This means that the advertised TDP is not just an arbitrary number they slap on the package.
  - pingyong 7y ago
    It's not an arbitrary number on Intel's CPUs either, it's just still not very useful. Or at least it's not useful as an indicator of some sort of technological progress. If you limit a 3900X to 3900 clock speeds and voltages, it's going to behave exactly the same.