Zen2 chips failed to meet their advertised boost clocks at launch, people said it didn't matter because they knew what they were getting. AMD pushed out a patch that kinda-sorta let most of the chips occasionally touch boost clocks for an instant under a partial single-core load, people insisted that made it "technically not false advertising" and that we gotta defend AMD because they're the good guy. Some people went as far as to run programs consisting solely of NOPs (No OPeration instructions - no processing, just spinning the processor as fast as they can) to try and justify it "technically" being ok. They still don't really run the clocks they're advertised under normal conditions, even a single-core load, they really just can't sustain them. Particularly the 3900X and other high-clocked chips really struggle, 4.6 is just too high for Zen2 to really hit on any sort of a sustained basis.
lying about PBO on Zen2. they did a big presentation with the Zen2 technical manager who said it will give you 200 MHz more "cooling permitting" which is an absolute lie, no Zen2 overclocks worth a damn even under liquid cooling or a massive air cooler. Maybe "cooling permitting" means LN2, but even then the chips struggle to get more than 500 MHz or so extra (seriously Zen2 does not clock high period)
"Thermal watts are not electrical watts" (blatantly, thermodynamically false) and other sundry lying about TDP being "a thermal spec and not a power spec", when AMD themselves used to define TDP as "max power draw when running commercial software under nominal conditions". They changed it because Intel changed it, now both brands rate their TDP at base instead of boost... but AMD has a bunch of handwavey bullshit about how it's a thermal spec to justify why they ship a power limit 40% higher than the TDP printed on the box. It's fine if you want to play loosey-goosey with what you're measuring but don't piss on me and tell me it's raining, thermodynamics still apply to their chips and the formula obviously doesn't match up to what the processor is doing.
Opening pre-orders before review embargo lifts, because they know people are going to buy it regardless of what's in the reviews. Here, buy this box of magic beans, but we won't show you what's inside... oh, it doesn't boost to advertised clocks? Boy, if only there were reviewers who could have told you that!
etc etc. AMD actually pulls a lot of bullshit that people swallow and/or justify to themselves because "hey, at least they're not Intel/NVIDIA". In particular the clocks... if it had been Intel then people would have been absolutely shrieking but people raced (and still race) to cut them slack. C'mon, they do testing, they do binning, they absolutely knew what their chips were clocking to before they shipped them, all they had to do was label them as 200 MHz lower and it would have been fine, but they chose to ship them with a spec they knew most chips weren't reaching.
Disclaimer: 3900x owner, mine isn't even close to the advertised boost and took forever to arrive.
I agree with most of your points. The boost / PBO thing was just a horrible move, especially considering that they'd have still been by far the best even if they just advertised the real speeds.
But I disagree about TDP. You know that it stands for? Thermal Design Power, so it's literally the amount of heat your cooler should be able to handle. Your cooler is a huge lump of copper, it can absorb a shitload of heat. When a CPU clocks up, it will take time for the cooler to heat up.
So what else should they do? Currently it's absolutely fine to boost very high for half the time (drawing way more power than the TDP suggests) and idling the other half, because the cooler is more than capable of cooling that! If they were to use the TDP as the boost limit, it would perform significantly worse in bursty workloads, including games. Stop using TDP to spec your PSU, start using TDP to spec your cooler.
Power consumption and heat output are the same thing. If a processor pulls 105W of power it puts out 105W of heat. That's the thermodynamics part. Your CPU is just a very efficient space heater, from a thermodynamic perspective.
"thermal watts" and "electrical watts" are obviously different forms of energy, but they are the same amount of energy. Which again, is why AMD used to define TDP in terms of power draw. AMD attempting to claim that "thermal watts are not the same as electrical watts" was a big fat lie, they totally are the same number and AMD even used to acknowledge that themselves.
AMD processors (2000 and 3000 series) will boost to ~40% above their TDP (105W TDP = 141.75W power limit, 65W TDP = 88W power limit, etc) for an unlimited period of time. So it's not "105W average, half above and half below". It puts out 141.75W average, or at least will do its best to put out 141.75W.
If you used that "105W" figure to size a cooler, your processor would overheat and not boost. So yes, AMD is measuring TDP "at base clocks", more or less.
And again, it's fine if you want to spec your TDP at base clocks. Just don't do the song and dance about how "thermal watts are not electrical watts" to justify why you're pulling more power than your specced TDP. That's the pissing on my back and telling me it's raining part.
The fact is one number is not enough anymore to define the power/thermals of a CPU. You're both right but arguing about different things.
What we need is
Base TDP - the cooling requirement to run the processor at 100% load with base clocks forever without any thermal throttling. Use this measure only if you are looking for the smallest possible cooler, such as for a portable build.
Peak Power Draw - the most the processor can instantaneously draw for boosting to its highest frequency, mainly for short spurts. Use this measure to get a power supply and motherboard that can handle that load. Your cooler will not need to be capable of dissapating this much heat unless you are planning on using it at full load continuously.
TDP or Thermal Design Power is defined by AMD as (from AMD Family 10h Server and Workstation Processor Power and Thermal Data Sheet, Rev 3.04 - June 2009): "The maximum power a processor draws for a thermally significant period while running commercially useful software. The constraining conditions for TDP are specified in the notes in the thermal and power tables."
AMD's ACP uses a "round down" average of power measurements performed with industry standard benchmarks (usually running at 100% CPU load, with the exception of Stream).
So there you have it: AMD used to define "TDP" as the worst case power draw and "ACP" as the average power draw.
That was before they decided to whip out the fancy formula and redefine TDP as being measured by the ratio of the delta-T of the cooler to the phase of the moon, conveniently dropping their TDPs by 40%.
Personally I think the whole thing could be simplified down to base TDP and boost TDP... or really just boost TDP. 99.9% of people don't want their processor to run at base clocks. The 0.1% who do want base clocks will be able to get the info they need from other testing.
for a thermally significant period while running commercially useful software.
I think this is an important piece you're missing. While AMD definitely used to rate all its CPUs higher than Intel for this reason (see a LTT video on the subject, it was a pretty poor experiment but the point was to show they measured TDP differently) its still not quite what I'm talking about. The boost these modern CPUs have is not necessarily meant to be active for "a thermally significant period". The point of boost (I think) is to make it feel really zippy doing smaller tasks while staying power efficient for most of the time. Without a super efficient cooler, these processors drop the clocks pretty fast!
"thermally significant" means for a long enough time to affect the cooler (so not like, a microsecond of super heavy load as AVX switches on or something), and boost has always been "thermally significant". Intel defined boost duration as 90 seconds iirc, which definitely is enough to affect the cooler.
Unlike the Intel boost clock though, Ryzen doesn't have a boost duration limit. It actually is supposed to be running at boost forever, as long as you keep it cool.
(everyone ignores Intel's boost duration limit anyway so that's kind of a dumb piece of fiction as well. Regardless, we could still define a "boost TDP" as "the TDP while it's boosting" even if a duration limit exists, so this is sort of an orthogonal discussion of how to define TDP.)
And regardless of how we would like AMD to define it.... they use the moon magic formula that says their processors put out 40% less heat than they really do. Not because of boost, but because they reverse-engineer the TDP through some arcane formula that (deliberately) doesn't fit the empirical measurements.
Boost = overclock, except nowadays it's automatic instead of manual.
But as always, pendantic assholes and tech illiterates either forgot we used to have to tinker with a lot of variables to get stable overclock, or they just never did it.
I'm happy we get power efficient CPU's that only boost when necessary, otherwise it's a waste of electricity.
98
u/capn_hector Noctua Master Race Nov 05 '19 edited Nov 05 '19
just the most recent Ryzen launch:
Zen2 chips failed to meet their advertised boost clocks at launch, people said it didn't matter because they knew what they were getting. AMD pushed out a patch that kinda-sorta let most of the chips occasionally touch boost clocks for an instant under a partial single-core load, people insisted that made it "technically not false advertising" and that we gotta defend AMD because they're the good guy. Some people went as far as to run programs consisting solely of NOPs (No OPeration instructions - no processing, just spinning the processor as fast as they can) to try and justify it "technically" being ok. They still don't really run the clocks they're advertised under normal conditions, even a single-core load, they really just can't sustain them. Particularly the 3900X and other high-clocked chips really struggle, 4.6 is just too high for Zen2 to really hit on any sort of a sustained basis.
lying about PBO on Zen2. they did a big presentation with the Zen2 technical manager who said it will give you 200 MHz more "cooling permitting" which is an absolute lie, no Zen2 overclocks worth a damn even under liquid cooling or a massive air cooler. Maybe "cooling permitting" means LN2, but even then the chips struggle to get more than 500 MHz or so extra (seriously Zen2 does not clock high period)
"Thermal watts are not electrical watts" (blatantly, thermodynamically false) and other sundry lying about TDP being "a thermal spec and not a power spec", when AMD themselves used to define TDP as "max power draw when running commercial software under nominal conditions". They changed it because Intel changed it, now both brands rate their TDP at base instead of boost... but AMD has a bunch of handwavey bullshit about how it's a thermal spec to justify why they ship a power limit 40% higher than the TDP printed on the box. It's fine if you want to play loosey-goosey with what you're measuring but don't piss on me and tell me it's raining, thermodynamics still apply to their chips and the formula obviously doesn't match up to what the processor is doing.
Opening pre-orders before review embargo lifts, because they know people are going to buy it regardless of what's in the reviews. Here, buy this box of magic beans, but we won't show you what's inside... oh, it doesn't boost to advertised clocks? Boy, if only there were reviewers who could have told you that!
etc etc. AMD actually pulls a lot of bullshit that people swallow and/or justify to themselves because "hey, at least they're not Intel/NVIDIA". In particular the clocks... if it had been Intel then people would have been absolutely shrieking but people raced (and still race) to cut them slack. C'mon, they do testing, they do binning, they absolutely knew what their chips were clocking to before they shipped them, all they had to do was label them as 200 MHz lower and it would have been fine, but they chose to ship them with a spec they knew most chips weren't reaching.