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Old 25th December 2010
guitarscn guitarscn is offline
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Default Why does OpenBSD run so hot?

So I got OpenBSD installed on a MacBook Pro and noticed from the start (default install) at the console login screen, if I just leave it that way for a couple minutes, my laptop gets hotter and hotter. And I can feel a burning sensation when I touch the case. As opposed to booting the native OS X, it runs much cooler and I don't feel heat emanating from beneath the keyboard up into my hands while I'm typing.

Is this a hardware thing? OS X runs much more apps by default and they are more memory/CPU intensive (I think) compared to the OpenBSD default install, so I've been inclined to believe it's some sort of hardware thing but was wondering if anyone more knowledgeable might be able to speculate on what's going on here.
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Old 25th December 2010
BSDfan666 BSDfan666 is offline
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Is this an x86 machine? if so, most OS's will scale the CPU clock rate, lowering the temperature.

On OpenBSD, you can do this manually setting the hw.setperf sysctl(1), or by configuring apmd(8) in /etc/rc.conf.local.

There was once a diff floating around the mailing lists to do automatic scaling in the kernel, but I'm not sure if it was committed.
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Old 25th December 2010
guitarscn guitarscn is offline
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Yes, it's x86. How come OpenBSD does not scale the CPU clock rate (by default)?
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Old 26th December 2010
BSDfan666 BSDfan666 is offline
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Because it requires processor support, Intel and AMD do it different, and to make matters worse.. each vendor has changed their method multiple times.

Not only that, but it's also equally complicated gathering the supported speeds.

Many people also prefer to not scale the clock rate, as it effects performance, it's usually only a concern for laptop users (..battery life).

As I said, try toggling that sysctl.. raising/lower, and compare it with hw.cpuspeed.
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Old 26th December 2010
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Scaling and power management come through ACPI. Your Mac follows it's own rules, rather than the standard.
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