# Black screen at boot process

## JuszR

I've recently emerged the power management modules in kernel (powersave, performance governor...) and now everytime i turn on the pc, it shows until "Waiting for udev..." then a black screen and i can see the login manager (slim). 

How to fix that?

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## audiodef

Can you pastebin your kernel config?

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## JuszR

http://pastebin.com/gMTDwfK0

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## audiodef

What option is this?

```

CONFIG_X86_ACPI_CPUFREQ_CPB=y

```

I use CPU freq scaling and I don't see that in my .config. Everything else I have in CPU freq scaling is identical to yours, though, and my .config works.

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## Hu

```
config X86_ACPI_CPUFREQ_CPB

    default y

    bool "Legacy cpb sysfs knob support for AMD CPUs"

    depends on X86_ACPI_CPUFREQ && CPU_SUP_AMD

    help

      The powernow-k8 driver used to provide a sysfs knob called "cpb"

      to disable the Core Performance Boosting feature of AMD CPUs. This

      file has now been superseeded by the more generic "boost" entry.

      By enabling this option the acpi_cpufreq driver provides the old

      entry in addition to the new boost ones, for compatibility reasons.
```

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## chithanh

If I had to guess, udev loads a KMS graphics driver module. If you have framebuffer console support built as module and not loaded, the screen will go dark, until X starts or the fbcon module is loaded.

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## JuszR

I've added fbcon to the automatic loaded modues and it worked.

Thank you.

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