4 ms·

Server parts are big chips (or a bunch of chiplets) running at fairly moderate clock speeds. For example your XCC CPU should have a die size in the 600-700 mm²

Server parts are big chips (or a bunch of chiplets) running at fairly moderate clock speeds. For example your XCC CPU should have a die size in the 600-700 mm² neighborhood for a power density of around 0.3 W/mm² (which neglects hotspots because probably half the CPU is cache, which does not consume half the power). Desktop parts like the 10900K can chug down 200+ W on a 200 mm² die, though that's basically impossible to cool. Even more reasonable CPUs like AMD's 5000 series run something like 40-50 W through an 80 mm² die, these are still hard to cool.

bayindirh 5y ago
This is a different and refreshing perspective. I've never looked from the perspective of W/mm². OTOH, the number I've given is calculated by eyeballing the per core internal thermistors, provided by lm_sensors (hence by CPU itself). So, per die sensors are probably reading somewhat lower numbers, but the core's cooking at 70 degrees C internally. Nevertheless, bigger die surface inevitably allows better heat conduction and reduces internal stresses considerably, when compared to a desktop part.
- megous 5y ago
  Desktop use is also very uneven, leading to a lot of large changes in temperature (35 -> 80 and back), which causes more material stress, than when everything is loaded evenly all the time. The same is true for electrical transients.
  - bayindirh 5y ago
    If you have a good cooler with lots of thermal capacity and good fan (like an Arctic Cooling or Noctua, nothing at the extreme end), the increase is very gradual. Also, short spikes in loads are well absorbed with minimal temperature changes. Nevertheless the numbers you mention are neither unrealistic, nor impossible in stock cooling and/or sustained load scenarios.
    - megous 5y ago
      5950X with the top of the line noctua cooler jumps from 35C to 80C very quickly when a single core is loaded at 100% (this is the worst case, because it leads to max voltage being applied to the CPU cores (because of boost to almost 5GHz), compared to loading all 16 cores at 100%, which will result in just 60˚C temperature sustained over long periods of full load). So interestingly, compiling the Linux kernel with 32 threads is less thermally straining on the CPU than browsing the web and a single page loading 10 different animated ads.
      - formerly_proven 5y ago
        This mirrors my experience with Zen 2 and 3 as well. Multi-core loads result in just a few W per core and decent temperatures, while few or single core loads push per-core power into the 12-16 W region and the temperature rise/fall is basically instant (brick-wall at 10 Hz update rate, though it's unclear what filtering is applied and how the CPU derives a single temperature from its probably numerous sensors), which suggests that they're not limited by the cooler, but rather by the thermal impedance from the active area to the cooler. The core itself is really tiny (iirc around 4 mm²)...
pdimitar 5y ago
This is my conundrum when pondering buying a Threadripper 3970x / 3975x Pro workstation: aren't those chips cooked very aggressively when loaded, even with very good coolers? Doesn't that mean that one day the CPU might just burn? I really want to buy a proper serious workstation and I can afford it in a few months but I keep wondering: is now the best time for it?
- jrockway 5y ago
  I wouldn't really worry about it. I have an overclocked 3970x and a Noctua air cooler keeps it much cooler than the Intel 6950X I had before (also aircooled, with an even larger Noctua cooler). Air cooling is more of a limit to how high an overclock you can get; normal operation will be no problem for any cooling system designed for Threadripper. There's never a good time to buy a new computer. It's always going to be obsolete before you open the box. Though in this case, one might wait for the Zen 3 Threadrippers.
  - pdimitar 5y ago
    Thanks for the feedback, it's reassuring. As other posters said, I am worried because it's a workstation which means it won't have consistent load, and material stress is much more destructive in the thermal conditions of expanding and contracting. So if in your ~8h workday your station gets stressed for 2 or so hours in irregular intervals, how destructive is that, objectively? -- As for the Zen 3 TRs, well, to be fair, I am not looking to blow $50k on a workstation. :) I am more interested how -- and if -- they will drive down the prices of the TR 3900 SKUs...
    - jrockway 5y ago
      It probably won't drive down prices that much. You won't want the old thing, and the incremental cost between generations is not the expensive part of a workstation. I have bought old parts before (to replace broken parts), and my experience is that the price didn't change much. What was a $130 motherboard when brand new, is $130 when a generation old. Does it make any sense? Nope. But that seems to be how it is. You won't spend $50,000 on a workstation just by using current-generation parts. I think when you see a workstation that costs that much, it's because it has multiple GPUs in them. Pro GPUs are always artificially overpriced, and given the GPU shortage, they're now even more overpriced. I did a quick pcpartpicker expedition and found that using last-gen parts saves you about $1000 on a $6000 32 core Threadripper workstation. I compared last-gen SSDs, consumer GPUs, processor, and motherboard, and picked relatively high-end parts. You will save more money by dropping to 24 (or heaven forbid, 16) cores, not getting an extreme motherboard, getting 64G of RAM instead of 128, etc. This could all be invalid in a few months. It is hard to separate "market is always crazy" from "this whole COVID thing is going on". Building a workstation during the pandemic was a pain -- I bought a used GPU, and didn't get ECC memory because nobody would sell me any. If you wait a year, that is likely to improve, and there will be newer hardware. But, if you need to do some computing between now and then, you don't have much choice but to buy what's available now, and it certainly makes for a very good computer.

bayindirh 5y ago

This is a different and refreshing perspective. I've never looked from the perspective of W/mm². OTOH, the number I've given is calculated by eyeballing the per core internal thermistors, provided by lm_sensors (hence by CPU itself). So, per die sensors are probably reading somewhat lower numbers, but the core's cooking at 70 degrees C internally. Nevertheless, bigger die surface inevitably allows better heat conduction and reduces internal stresses considerably, when compared to a desktop part.

megous 5y ago
Desktop use is also very uneven, leading to a lot of large changes in temperature (35 -> 80 and back), which causes more material stress, than when everything is loaded evenly all the time. The same is true for electrical transients.
- bayindirh 5y ago
  If you have a good cooler with lots of thermal capacity and good fan (like an Arctic Cooling or Noctua, nothing at the extreme end), the increase is very gradual. Also, short spikes in loads are well absorbed with minimal temperature changes. Nevertheless the numbers you mention are neither unrealistic, nor impossible in stock cooling and/or sustained load scenarios.
  - megous 5y ago
    5950X with the top of the line noctua cooler jumps from 35C to 80C very quickly when a single core is loaded at 100% (this is the worst case, because it leads to max voltage being applied to the CPU cores (because of boost to almost 5GHz), compared to loading all 16 cores at 100%, which will result in just 60˚C temperature sustained over long periods of full load). So interestingly, compiling the Linux kernel with 32 threads is less thermally straining on the CPU than browsing the web and a single page loading 10 different animated ads.
    - formerly_proven 5y ago
      This mirrors my experience with Zen 2 and 3 as well. Multi-core loads result in just a few W per core and decent temperatures, while few or single core loads push per-core power into the 12-16 W region and the temperature rise/fall is basically instant (brick-wall at 10 Hz update rate, though it's unclear what filtering is applied and how the CPU derives a single temperature from its probably numerous sensors), which suggests that they're not limited by the cooler, but rather by the thermal impedance from the active area to the cooler. The core itself is really tiny (iirc around 4 mm²)...

pdimitar 5y ago

This is my conundrum when pondering buying a Threadripper 3970x / 3975x Pro workstation: aren't those chips cooked very aggressively when loaded, even with very good coolers? Doesn't that mean that one day the CPU might just burn? I really want to buy a proper serious workstation and I can afford it in a few months but I keep wondering: is now the best time for it?

jrockway 5y ago
I wouldn't really worry about it. I have an overclocked 3970x and a Noctua air cooler keeps it much cooler than the Intel 6950X I had before (also aircooled, with an even larger Noctua cooler). Air cooling is more of a limit to how high an overclock you can get; normal operation will be no problem for any cooling system designed for Threadripper. There's never a good time to buy a new computer. It's always going to be obsolete before you open the box. Though in this case, one might wait for the Zen 3 Threadrippers.
- pdimitar 5y ago
  Thanks for the feedback, it's reassuring. As other posters said, I am worried because it's a workstation which means it won't have consistent load, and material stress is much more destructive in the thermal conditions of expanding and contracting. So if in your ~8h workday your station gets stressed for 2 or so hours in irregular intervals, how destructive is that, objectively? -- As for the Zen 3 TRs, well, to be fair, I am not looking to blow $50k on a workstation. :) I am more interested how -- and if -- they will drive down the prices of the TR 3900 SKUs...
  - jrockway 5y ago
    It probably won't drive down prices that much. You won't want the old thing, and the incremental cost between generations is not the expensive part of a workstation. I have bought old parts before (to replace broken parts), and my experience is that the price didn't change much. What was a $130 motherboard when brand new, is $130 when a generation old. Does it make any sense? Nope. But that seems to be how it is. You won't spend $50,000 on a workstation just by using current-generation parts. I think when you see a workstation that costs that much, it's because it has multiple GPUs in them. Pro GPUs are always artificially overpriced, and given the GPU shortage, they're now even more overpriced. I did a quick pcpartpicker expedition and found that using last-gen parts saves you about $1000 on a $6000 32 core Threadripper workstation. I compared last-gen SSDs, consumer GPUs, processor, and motherboard, and picked relatively high-end parts. You will save more money by dropping to 24 (or heaven forbid, 16) cores, not getting an extreme motherboard, getting 64G of RAM instead of 128, etc. This could all be invalid in a few months. It is hard to separate "market is always crazy" from "this whole COVID thing is going on". Building a workstation during the pandemic was a pain -- I bought a used GPU, and didn't get ECC memory because nobody would sell me any. If you wait a year, that is likely to improve, and there will be newer hardware. But, if you need to do some computing between now and then, you don't have much choice but to buy what's available now, and it certainly makes for a very good computer.