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Can anyone with experience explain why the frequency of processors has basically stalled since hitting 3.x Ghz? I assume there is some kind of physical barrier

by swalsh 14y ago

Can anyone with experience explain why the frequency of processors has basically stalled since hitting 3.x Ghz? I assume there is some kind of physical barrier, but i'm not sure what it is.

anigbrowl 14y ago
They tend to overheat past that point in normal computers. Enthusiasts can get production chips running at up to 6GHz, but at that point they're having to use things like liquid nitrogen pumps. A passive radiator with an air fan can only conduct away so much heat. My newest PC (A core i7 or something, I forget exactly what now) has a heatsink that's bigger than my fist.
- zokier 14y ago
  I don't think the reason to use LN2 (liquid nitrogen) in extreme overclocking is because of the added heat generation. I bet water cooling (which is very "mainstream" compared to the more extreme solutions) could easily handle the extra heat. Afaik you actually need to reach very low temperatures to get the silicon work properly at the high speeds (I guess it has something to do with thermal noise and conductivity, but that's just guessing). And that is imho a sign that it's not just a power consumption / clockspeed tradeoff, but instead there are actually limits on how high you can go at room temperature.
Jtsummers 14y ago
Temperatures mainly. CPUs were approaching 4GHz a decade ago, but the power consumption and temperature output made higher speeds (and even those speeds) impractical. Multicore at those speeds would've (again) been power-wise impractical, so it made more sense to drop the speeds and have 2-4 cores until process improvements allowed clock speeds and core counts to both be higher.
- sliverstorm 14y ago
  Multicore at those speeds... In addition to power concerns of many fast cores on one chip, server chips (the multicore champions) tend to be larger dies, and place higher value on MTBF. I believe both of these factors work against super high frequency server offerings.
  - greedo 14y ago
    IBM's Power6 and 7 PowerPC cpus have easily exceeded 4GHz and even hit 5GHz for a few years. These are normally used in their AIX platforms.
    - sliverstorm 14y ago
      Right, and that makes sense. Larger dies are primarily a cost issue; they reduce yield, which increases cost per functional die. More development effort spent on MTBF is a resource issue; work spent improving MTBF is work not spent improving operating frequency, but with enough resources (money) it doesn't have to be a problem. I could be wrong on this, but I believe IBM's AIX line is not cheap, if you see where I'm going with this.
      - greedo 14y ago
        You're definitely going in the right direction; Power5/6/7 hardware is very pricey. I'm amazed that in this day and age, AIX still has a place in many companies, and slightly perturbed that I have to maintain it. I'd much rather have the applications running under RHEL.
Jach 14y ago
Besides the physical limits, for practical reasons clock speed shouldn't be the only thing one tries to optimize and a faster clockspeed doesn't imply a faster processor. http://en.wikipedia.org/wiki/Megahertz_myth http://en.wikipedia.org/wiki/Megahertz_myth More to the point, I wouldn't be surprised if there's already an Intel processor on the market with overall better performance than this new thing while having less cores and/or GHz.

by swalsh 14y ago

Can anyone with experience explain why the frequency of processors has basically stalled since hitting 3.x Ghz? I assume there is some kind of physical barrier, but i'm not sure what it is.

anigbrowl 14y ago

They tend to overheat past that point in normal computers. Enthusiasts can get production chips running at up to 6GHz, but at that point they're having to use things like liquid nitrogen pumps. A passive radiator with an air fan can only conduct away so much heat. My newest PC (A core i7 or something, I forget exactly what now) has a heatsink that's bigger than my fist.

zokier 14y ago
I don't think the reason to use LN2 (liquid nitrogen) in extreme overclocking is because of the added heat generation. I bet water cooling (which is very "mainstream" compared to the more extreme solutions) could easily handle the extra heat. Afaik you actually need to reach very low temperatures to get the silicon work properly at the high speeds (I guess it has something to do with thermal noise and conductivity, but that's just guessing). And that is imho a sign that it's not just a power consumption / clockspeed tradeoff, but instead there are actually limits on how high you can go at room temperature.

Jtsummers 14y ago

Temperatures mainly. CPUs were approaching 4GHz a decade ago, but the power consumption and temperature output made higher speeds (and even those speeds) impractical. Multicore at those speeds would've (again) been power-wise impractical, so it made more sense to drop the speeds and have 2-4 cores until process improvements allowed clock speeds and core counts to both be higher.

sliverstorm 14y ago
Multicore at those speeds... In addition to power concerns of many fast cores on one chip, server chips (the multicore champions) tend to be larger dies, and place higher value on MTBF. I believe both of these factors work against super high frequency server offerings.
- greedo 14y ago
  IBM's Power6 and 7 PowerPC cpus have easily exceeded 4GHz and even hit 5GHz for a few years. These are normally used in their AIX platforms.
  - sliverstorm 14y ago
    Right, and that makes sense. Larger dies are primarily a cost issue; they reduce yield, which increases cost per functional die. More development effort spent on MTBF is a resource issue; work spent improving MTBF is work not spent improving operating frequency, but with enough resources (money) it doesn't have to be a problem. I could be wrong on this, but I believe IBM's AIX line is not cheap, if you see where I'm going with this.
    - greedo 14y ago
      You're definitely going in the right direction; Power5/6/7 hardware is very pricey. I'm amazed that in this day and age, AIX still has a place in many companies, and slightly perturbed that I have to maintain it. I'd much rather have the applications running under RHEL.

Jach 14y ago

Besides the physical limits, for practical reasons clock speed shouldn't be the only thing one tries to optimize and a faster clockspeed doesn't imply a faster processor. http://en.wikipedia.org/wiki/Megahertz_myth http://en.wikipedia.org/wiki/Megahertz_myth More to the point, I wouldn't be surprised if there's already an Intel processor on the market with overall better performance than this new thing while having less cores and/or GHz.