Strange CPU speeds



  • Ive just started playing around with the Source SDK to make a test Half-Life 2 mod. On occasions when i opened the mod the console reported rather odd CPU speeds.

    Now im pretty sure i this is right: 2 CPUs, Frequency: 2.1 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Suddenly my CPU gained a huge boost in speed: 2 CPUs, Frequency: 27.2 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Then got rather slow: 2 CPUs, Frequency: -22926.5 Mhz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV






  • Slow? It got really, really fast and overflowed a signed integer because of it :)





  • I see the same kind of thing in Counter-Strike: Source's console every time I start it.  Usually it reports the proper 2.0GHz - but sometimes it's -14 GHz, or +17GHz.  I thought at first it was a cpu frequency scaling issue (speedstep or whatever it's called screwing with the CPU measurement when I'm on batteries) but it happens when I'm on AC power, so unless speedstep doesn't get disabled on AC power (it should, right?) then it's not that.



  • "so unless speedstep doesn't get disabled on AC power (it should, right?) then it's not that."

    Not necessarily. Check control panel/power or the utility that came with the laptop



  • @Heron said:

    so unless speedstep doesn't get disabled on AC power (it should, right?) then it's not that.
    I would be surprised if it was disabled on AC - it's enabled on my desktop computer, which runs at 1,6GHz normally, but jumps to 2,6GHz when I do serious work with it.



  • @CrouchSoft said:

    Ive just started playing around with the Source SDK to make a test Half-Life 2 mod. On occasions when i opened the mod the console reported rather odd CPU speeds.

    Now im pretty sure i this is right: 2 CPUs, Frequency: 2.1 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Suddenly my CPU gained a huge boost in speed: 2 CPUs, Frequency: 27.2 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Then got rather slow: 2 CPUs, Frequency: -22926.5 Mhz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Ah, you're using a dual-core system. It's probably estimating the CPU speed using the TSC register, which records the number of clock ticks since the last reset. Unfortunately, on a dual core system each core has its own TSC, and while they start off roughly syncronised they gradually get out of sync as time passes for various reasons. When a process that uses the TSC register moves from one core to the other, you can get all sorts of interesting results. (Some Googling suggests that Speedstep tends to cause this sort of desync on Intel processors, and that AMD processors have more subtle causes of the issue. If you want something really interesting, you should see what happens if you accidentally force the Linux kernel to use the TSC for the system clock on a dual-core AMD chip...)



  • @CrouchSoft said:

    Ive just started playing around with the Source SDK to make a test Half-Life 2 mod. On occasions when i opened the mod the console reported rather odd CPU speeds.

    Now im pretty sure i this is right: 2 CPUs, Frequency: 2.1 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Suddenly my CPU gained a huge boost in speed: 2 CPUs, Frequency: 27.2 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Then got rather slow: 2 CPUs, Frequency: -22926.5 Mhz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    The negative figures are the really awesome ones. It must mean it's undergoing a negative number of cycles in every positive second, or equivalently, a positive number of cycles in every NEGATIVE second. In other words, you get the result BEFORE you give it the instructions! With that (well, and enough storage), you can do ANYTHING.



  • @m0ffx said:

    @CrouchSoft said:

    Ive just started playing around with the Source SDK to make a test Half-Life 2 mod. On occasions when i opened the mod the console reported rather odd CPU speeds.

    Now im pretty sure i this is right: 2 CPUs, Frequency: 2.1 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Suddenly my CPU gained a huge boost in speed: 2 CPUs, Frequency: 27.2 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Then got rather slow: 2 CPUs, Frequency: -22926.5 Mhz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    The negative figures are the really awesome ones. It must mean it's undergoing a negative number of cycles in every positive second, or equivalently, a positive number of cycles in every NEGATIVE second. In other words, you get the result BEFORE you give it the instructions! With that (well, and enough storage), you can do ANYTHING.

    You assume a negative second is time reversed. :)



  • @dhromed said:

    @m0ffx said:
    @CrouchSoft said:

    Ive just started playing around with the Source SDK to make a test Half-Life 2 mod. On occasions when i opened the mod the console reported rather odd CPU speeds.

    Now im pretty sure i this is right: 2 CPUs, Frequency: 2.1 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Suddenly my CPU gained a huge boost in speed: 2 CPUs, Frequency: 27.2 Ghz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    Then got rather slow: 2 CPUs, Frequency: -22926.5 Mhz,  Features: GenuineIntel SSE SSE2 MMX RDTSC CMOV FCMOV

    The negative figures are the really awesome ones. It must mean it's undergoing a negative number of cycles in every positive second, or equivalently, a positive number of cycles in every NEGATIVE second. In other words, you get the result BEFORE you give it the instructions! With that (well, and enough storage), you can do ANYTHING.

    You assume a negative second is time reversed. :)

    Or said a different way, that it is not in fact [url=http://www.imdb.com/title/tt0105793/quotes]sucking your will to live[/url].


Log in to reply
 

Looks like your connection to What the Daily WTF? was lost, please wait while we try to reconnect.