# Do desktop users need ACPI?

## Joseph K.

My short question is: can I safely remove ACPI from the kernel (under Power Management) and USE=-acpi?

My main concern is that in the kernel configuration, there is a big warning about disabling Thermal Zones for your processor.  Well, I've had it enabled probably for ever, but then today realised that I never added the acpid script to the default runlevel anyway.

The only power-saving feature I'm interested in is DPMS for the monitor, which I assume does not require ACPI.

The nvidia-drivers package has optional support for ACPI: does anyone know what features this provides?

This is mostly of academic interest to me: ACPI is posing no problem for me, I'd just rather remove it if I don't need it.  Thanks, cheers.

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## Monkeh

ACPI is much more than just power management. Any modern system pretty much requires it, many won't work at all without it. You do however, only need kernel support. Nothing else needs to care about it.

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## albright

In particular, acpi assigns interrupts ... I know because when I

got too smart and thought I'd just get rid of it, my sata drives

caused an interrupt conflict that prevented booting. Acpi fixed

that right up  :Smile: 

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## i92guboj

As people say, ACPI is more than just power management.

Things like cpu throttling, hardware monitoring (which in turn can save you some money and prevent damage due to overheat if a fan fails...). Not to speak about my preferred thing: if you don't use acpi and accidentally press the power button, all your filesystems will be trashed, which in turn may mean data loss, of even a completely trashed filesystem. With the acpi daemon running, linux will correctly turn off all the running services and umount all your filesystems, preventing data loss in the way.

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## Monkeh

 *i92guboj wrote:*   

> As people say, ACPI is more than just power management.
> 
> Things like cpu throttling, hardware monitoring (which in turn can save you some money and prevent damage due to overheat if a fan fails...). Not to speak about my preferred thing: if you don't use acpi and accidentally press the power button, all your filesystems will be trashed, which in turn may mean data loss, of even a completely trashed filesystem. With the acpi daemon running, linux will correctly turn off all the running services and umount all your filesystems, preventing data loss in the way.

 

By accidentally press, you mean hold down for eight seconds, right?  :Wink: 

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## Simba7

 *Monkeh wrote:*   

> By accidentally press, you mean hold down for eight seconds, right? 

 

You mean four?  :Wink: 

But I've bumped into this. Things work ALOT better with ACPI. Without it, things tend to go absolutely nuts. You definitely don't want to disable this on a laptop without it burning up and/or draining your battery in a 1/2 hour.

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## i92guboj

 *Monkeh wrote:*   

>  *i92guboj wrote:*   As people say, ACPI is more than just power management.
> 
> Things like cpu throttling, hardware monitoring (which in turn can save you some money and prevent damage due to overheat if a fan fails...). Not to speak about my preferred thing: if you don't use acpi and accidentally press the power button, all your filesystems will be trashed, which in turn may mean data loss, of even a completely trashed filesystem. With the acpi daemon running, linux will correctly turn off all the running services and umount all your filesystems, preventing data loss in the way. 
> 
> By accidentally press, you mean hold down for eight seconds, right? 

 

No. I mean accidentally. That depends on a number of factors, depending on both hardware and software. If your OS is not acpi capable, the normal behavior is frequently that: your pc shuts down when you press that button.

What you say (hold the button a number of seconds) is a way to tell the hardware to force the power off, overriding the OS acpi functions. But that is only relevant if the OS is acpi capable. If that is not the case, it just shuts down instantly in most cases.

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## Cyker

Power button behaviour varies quite wildly and depends on BIOS configuration if ACPI is not being used...

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## bunder

another thing acpi is good for is turning off / rebooting your pc... if you don't have acpi, the kernel will tell you to manually power off.   :Shocked: 

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## Joseph K.

I assume there is some confusion between ACPI and APIC going on here.

I have disabled ACPI and everything works fine, including hardware monitoring and fan control (controlled by the I2C bus).  The only convenience that I've lost is that, as bunder mentioned, I have to power-off manually (it still reboots from software).  So whilst I think you'd be mad to disable ACPI on a laptop, I'm not convinced that it offers desktop users anything really useful.

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## Monkeh

 *Joseph K. wrote:*   

> I assume there is some confusion between ACPI and APIC going on here.
> 
> I have disabled ACPI and everything works fine, including hardware monitoring and fan control (controlled by the I2C bus).  The only convenience that I've lost is that, as bunder mentioned, I have to power-off manually (it still reboots from software).  So whilst I think you'd be mad to disable ACPI on a laptop, I'm not convinced that it offers desktop users anything really useful.

 

How many CPUs do you have?

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## Joseph K.

 *Monkeh wrote:*   

> How many CPUs do you have?

 

It's a Core2 Duo.

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## Cyker

Well, in theory, ACPI things you loose *can* include: lm_sensors, powernow (Speedstep too?) and lots of other powersaving stuff (Some can still be accessed via APM, but it seems a lot of mobos don't support APM now?), APIC support, HPET support, SMP support (If the mobo doesn't support MPS).

Emphasis on the *can* and *in theory*.

Lots of mobos still work with lm_sensors, even without ACPI, although some sensors may go missing or be found in different places.

SMP requires an advanced interrupt handler, so if APIC doesn't work and MPS fallback isn't working then there's the possibility multi-core/socket CPUs systems will only find one CPU.

The main loss is powersaving stuff really, 'tho much of that can still be done via APM, assuming mobo support exists...

Most of this isn't technically necessary for operation of the compy 'tho.

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## Joseph K.

 *Cyker wrote:*   

> Well, in theory, ACPI things you loose *can* include: lm_sensors, powernow (Speedstep too?) and lots of other powersaving stuff (Some can still be accessed via APM, but it seems a lot of mobos don't support APM now?), APIC support, HPET support, SMP support (If the mobo doesn't support MPS).

 

Yeah, now that I've looked at the ACPI specification I can see the references to APIC, HPET, etc.  Even some PCI-E stuff.  OK, I guess I had the confusion after all.   :Smile: 

Well, if it does more than power management and is crucial for the operation of some computers, then I think being under PM in the kernel is a little misleading.  Maybe something about the importance of it should be in the installation manual or in the Wiki?  I only did a cursory scan, but I couldn't find anything that suggests that it's necessary for anything other than PM.

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## Cyker

It's probably there for 'historical reasons' (i.e. when ACPI came out it was just a newer buggier version of APM. It's 'evolved' to be more, but has stayed in the same place.)

As for importance, it's very relative.

I still have a pre-ACPI 'board here and that works perfectly well without ACPI support  :Wink: 

I even disabled APM too and just relied on the BIOS to spin down the HDs and fans.

But yeah, there is that sort of un-mentioned assumption floating around that you should know to turn it on without actually being told.

Sadly, there's alot of things like that in Linuxland still...

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