Reaching for Turbo: Aligning Perception with AMD’s Frequency Metrics
by Dr. Ian Cutress on September 17, 2019 10:00 AM ESTDo Manufacturers Guarantee Turbo Frequencies?
The question: ‘do manufacturers guarantee turbo frequencies?’ seems like it has an obvious answer to a lot of people. I performed a poll on my private twitter, and the voting results (700+) were astonishing.
Testing my audience's knowledge. Is the CPU Turbo Frequency on a desktop processor guaranteed by the manufacturer? Yes or No? [POLL]
— Dr. Ian Cutress (@IanCutress) September 12, 2019
31% of people said yes, 69% of people said no.
The correct answer is No, Turbo is never guaranteed.
To clarify, we need to define guarantee:
"A formal assurance that certain conditions will be fulfilled - if pertaining to a product, then that product will be repaired or replaced if not the specified quality."
This means that under a guarantee, the manufacturer would be prepared to repair or replace the product if it did not meet that guarantee. By that definition, Turbo is in no way under the guarantee from the manufacturer and does not fall under warranty.
Both AMD and Intel guarantee four things with their hardware: core counts, base frequency, peak power consumption at that base frequency (in essence, the TDP, even though strictly speaking TDP isn’t a measure of power consumption, but it is approximate), and the length of time those other items are guaranteed to work (usually three years in most locales). If you buy a 6 core CPU and only four cores work, you can get it replaced. If that six core CPU does not hit the base frequency under standard operations (standard is defined be Intel and AMD here, usually with a stock cooler, new paste, a clean chassis with active airflow of a minimum rate, and a given ambient temperature), then you can get it replaced.
Turbo, in this instance, is aspirational. We typically talk about things like ‘a 4.4 GHz Turbo frequency’, when technically we should be stating ‘up to 4.4 GHz Turbo frequency’. The ‘up to’ part is just as important as the rest, and the press (me included) is guilty of not mentioning the fact more often. Both Intel and AMD state that their processors under normal conditions should hit the turbo frequency, and both companies actively promote frequency enhancing tools such as aggressive power modes or better turbo profiles, but in no way is any of this actually guaranteed.
Yes, it does kind of suck (that’s the technical term). Both companies market their turbo frequencies loudly, proudly, and sometimes erroneously. Saying something is the ‘first X GHz’ processor only really means something if you can actually get into a position where that frequency is guaranteed. Unscrupulous retailers even put the turbo frequency as the highlight in their marketing material. Trying to explain to the casual user that this turbo frequency, this value that’s plastered everywhere, isn’t actually covered by the warranty, isn’t a good way to encourage them to get a processor.
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Smell This - Wednesday, September 18, 2019 - link
{ s-n-i-c-k-e-r }
BurntMyBacon - Wednesday, September 18, 2019 - link
Electron migration is generally considered to be the result of momentum transfer from the electrons, which move in the applied electric field, to the ions which make up the lattice of the interconnect material.Intuitively speaking, raising the frequency would proportionally increase the number of pulses over a given time, but the momentum (number of electrons) transferred per pulse would remain the same. Conversely, raising the voltage would proportionally increase the momentum (number of electrons) per pulse, but not the number of pulses over a given time. To make an analogy, raising the frequency is like moving your sandpaper faster while raising your voltage is like using coarser grit sandpaper at the same speed.
You might assume that if the total number of electrons are the same, then the wear will be the same? However, there is a certain amount of force required to dislodge an atom (or multiple atoms) from the interconnect material lattice. Though the concept is different, you can simplistically think of it like stationary friction. Increasing the voltage increases the force (momentum) from each pulse which could overcome this resistance where nominal voltages may not be enough. Also, increasing voltage has a larger affect on heat produced than increasing frequency. Adding heat energy into the system may lower the required force to dislodge the atom(s). If the nominal voltage is unable or only intermittently able to exceed the required force, then raising the frequency will have little effect compared to raising the voltage. That said, continuous strain will probably weaken the resistance over time, but it is likely that this still less significant than increasing voltage. Based on this, I would expect (read my opinion) four things:
1) Electron migration becomes exponentially worse the farther you exceed specifications (Though depending on where your initial durability is it may not be problematic)
2) The rate of electron migration is not constant. Holding all variables constant, it likely increases over time. That said, there are likely a lot of process specific variables that determine how quickly the rate increases.
3) Increasing voltage has a greater affect on electron migration than frequency. Increasing frequency alone may be considered far more affordable from a durability standpoint than increases that require significant voltage.
4) Up to a point, better cooling will likely reduce electron migration. We are already aware that increased heat physically expands the different materials in the semiconductor at different rates. It is likely that increased heat energy in the system also makes it easier to dislodge atoms from their lattice. Reducing this heat build-up should lessen the effect here.
Some or all of these may be partially or fully incorrect, but this is where my out of date intuition from limited experience in silicon fabrication takes me.
eastcoast_pete - Wednesday, September 18, 2019 - link
Thanks Ian! And, as mentioned, would also like to hear from you or Ryan on the same for GPUs. With lots of former cryptomining cards still in the (used) market, I often wonder just how badly those GPUs were abused in their former lifes.nathanddrews - Tuesday, September 17, 2019 - link
My hypothesis is that CPUs are more likely to outlive their usefulness long before a hardware failure. CPUs failing due to overclocking is not something we hear much about - I'm thinking it's effectively a non-issue. My i5-3570K has been overclocked at 4.2GHz on air for 7 years without fault. I don't think it has seen any time over 60C. That said, as a CPU, it has nearly exhausted its usefulness in gaming scenarios due to lack of both speed and cores.What would cause a CPU to "burn out" that hasn't already been accounted for via throttling, auto-shutdown procedures, etc.?
dullard - Tuesday, September 17, 2019 - link
Thermal cycling causes CPU damage. Different materials expand at different rates when they heat, eventually this fatigue builds up and parts begin to crack. The estimated failure rate for a CPU that never reaches above 60°C is 0.1% ( https://www.dfrsolutions.com/hubfs/Resources/servi... ). So, in that case, you are correct that your CPU will be just fine.But, now CPUs are reaching 100°C, not 60°C. That higher temperature range doubles the temperature range the CPUs are cycling through. Also, with turbo kicking on/off quickly, the CPUs are cycling more often than before. https://encrypted-tbn0.gstatic.com/images?q=tbn:AN...
GreenReaper - Wednesday, September 18, 2019 - link
Simple solution: run BOINC 24/7, keeps it at 100°C all the time!I'm sure this isn't why my Surface Pro isn't bulging out of its case on three sides...
Death666Angel - Thursday, September 19, 2019 - link
Next up: The RGB enabled hair dryer upgrade to stop your precious silicon from thermal cycling when you shut down your PC!mikato - Monday, September 23, 2019 - link
Now I wonder how computer parts had an RGB craze before hair dryers did. Have there been andy RGB hair dryers already?tygrus - Saturday, September 28, 2019 - link
The CPU temperature sensors have changed type and location. Old sensors were closer to the surface temperature just under the heatsink (more of an average or single spot assumed to be the hottest). Now its the highest of multiple sensors built into the silicon and indicates higher temperatures for the same power&area than before. There is always a temperature gradient from the hot spots to where heat is radiated.eastcoast_pete - Wednesday, September 18, 2019 - link
For me, the key statement in your comment is that your Sandy Bridge i7 rarely if ever went above 60 C. That is a perfectly reasonable upper temperature for a CPU. Many current CPUs easily get 50% hotter, and that's before any overclocking and overvolting. For GPUs, it even worse; 100 - 110 C is often considered "normal" for "factory overclocked" cards.