4 ms·

This is common on multicore Intel chips as well -- the chip itself has a max heat profile that it can't exceed, so if several of the cores are quiet a single co

This is common on multicore Intel chips as well -- the chip itself has a max heat profile that it can't exceed, so if several of the cores are quiet a single core can go much higher than it normally can, indefinitely if it remains the primary worker and there is enough heat dissipation. The i5 in the new Mac Air runs at 1.3Ghz if both cores are active, but if a single core is active and the environment isn't too hot and ventilation is working, a single core can hit 2.6Ghz. Which is quite humorous -- you might have much better real life performance simply disabling a core. EDIT: To clarify, I replied because of the supposition by the parent that this turbo mode is "for a few milliseconds". In actual practice it is usually a very significant contributor to performance on modern chips, and as mentioned can be indefinite in some circumstances. Ergo, dramatically more important than implied.

drcode 13y ago
Right, but intel usually doesn't create press releases that ONLY mention the turbo speed, as if that is the only meaningful speed metric.
- corresation 13y ago
  AMD is behind, and they'll use gimmicks where they can. Though since nvidia came up elsewhere, note that nvidia effectively advertises their "turbo" speed as the base and max speed, but in practice you'll often find it regulated to lower speeds for heat reasons. In this case, however, it's an 8-core chip. Very few current workloads will saturate 8 cores (even on heavily taxed database servers), meaning that there is a good chance there is always thermal availability for individual cores (and thus individual threads) to be run at 5Ghz.
  - bad_user 13y ago
    > *Very few current workloads will saturate 8 cores (even on heavily taxed database servers) It depends. Some tasks, such as processing incoming HTTP requests and building responses, such as web servers do - are embarrassingly parallelizable. And if you have an architecture that scales horizontally, with enough network bandwidth, you can saturate how many cores you want.
    - corresation 13y ago
      Oh for sure there are cases that might saturate all cores. They're just incredibly rare, even on machines that are working at "100%". The case of web servers is an interesting one because benchmarks seldom see them actually running at 100% despite putting all of their combined resources at a problem -- there is usually something else synchronously slowing the flow, or a simple bottleneck like Gbps networking. Even on virtualization servers, one generally leaves enough headroom that the machine is nowhere near saturated.
    - deleted 13y ago
      [deleted]
bentcorner 13y ago
> Which is quite humorous -- you might have much better real life performance simply disabling a core. Does this have any implications when designing software? (e.g., do things on a single processor in certain situations because it might be faster?)
- kayoone 13y ago
  Not really. In most cases your software is single threaded anyway, unless you implement some sort of parallelism yourself and when you do that it usually should make sense. But in the end its the OS thats shuffles the threads around on the cores. If you disable a core, the others can run faster reaching higher clock speeds which might or might not be benefical to your program depending on the work it does.

drcode 13y ago

Right, but intel usually doesn't create press releases that ONLY mention the turbo speed, as if that is the only meaningful speed metric.

corresation 13y ago
AMD is behind, and they'll use gimmicks where they can. Though since nvidia came up elsewhere, note that nvidia effectively advertises their "turbo" speed as the base and max speed, but in practice you'll often find it regulated to lower speeds for heat reasons. In this case, however, it's an 8-core chip. Very few current workloads will saturate 8 cores (even on heavily taxed database servers), meaning that there is a good chance there is always thermal availability for individual cores (and thus individual threads) to be run at 5Ghz.
- bad_user 13y ago
  > *Very few current workloads will saturate 8 cores (even on heavily taxed database servers) It depends. Some tasks, such as processing incoming HTTP requests and building responses, such as web servers do - are embarrassingly parallelizable. And if you have an architecture that scales horizontally, with enough network bandwidth, you can saturate how many cores you want.
  - corresation 13y ago
    Oh for sure there are cases that might saturate all cores. They're just incredibly rare, even on machines that are working at "100%". The case of web servers is an interesting one because benchmarks seldom see them actually running at 100% despite putting all of their combined resources at a problem -- there is usually something else synchronously slowing the flow, or a simple bottleneck like Gbps networking. Even on virtualization servers, one generally leaves enough headroom that the machine is nowhere near saturated.
  - deleted 13y ago
    [deleted]

bentcorner 13y ago

> Which is quite humorous -- you might have much better real life performance simply disabling a core. Does this have any implications when designing software? (e.g., do things on a single processor in certain situations because it might be faster?)

kayoone 13y ago
Not really. In most cases your software is single threaded anyway, unless you implement some sort of parallelism yourself and when you do that it usually should make sense. But in the end its the OS thats shuffles the threads around on the cores. If you disable a core, the others can run faster reaching higher clock speeds which might or might not be benefical to your program depending on the work it does.