# Which Real Time Clock opts to enable?

## audiodef

How do I know what, if any, Real Time Clock options to set in the kernel under Device Drivers -> Real Time Clock, with an rt-kernel? 

cat /proc/cpuinfo:

```

processor   : 0

vendor_id   : AuthenticAMD

cpu family   : 15

model      : 37

model name   : AMD Opteron(tm) Processor 248

stepping   : 1

cpu MHz      : 2200.000

cache size   : 1024 KB

fpu      : yes

fpu_exception   : yes

cpuid level   : 1

wp      : yes

flags      : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt lm 3dnowext 3dnow rep_good extd_apicid pni lahf_lm

bogomips   : 4420.83

TLB size   : 1024 4K pages

clflush size   : 64

cache_alignment   : 64

address sizes   : 40 bits physical, 48 bits virtual

power management: ts fid vid ttp

processor   : 1

vendor_id   : AuthenticAMD

cpu family   : 15

model      : 37

model name   : AMD Opteron(tm) Processor 248

stepping   : 1

cpu MHz      : 2200.000

cache size   : 1024 KB

fpu      : yes

fpu_exception   : yes

cpuid level   : 1

wp      : yes

flags      : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt lm 3dnowext 3dnow rep_good extd_apicid pni lahf_lm

bogomips   : 4419.44

TLB size   : 1024 4K pages

clflush size   : 64

cache_alignment   : 64

address sizes   : 40 bits physical, 48 bits virtual

power management: ts fid vid ttp

```

----------

## completemongerel

under  Device Drivers > delselect 'Real Time Clock'. 

then    Device Drivers > Character Devices select 'Enhanced Real Time Clock Support'

Note. Enhanced Real Time Clock Support' under character devices will not appear until 'Real Time Clock' is deselected.

i think that's what you need. if a module rtc nedds to be added to your modules array.

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## audiodef

What's the difference between rtc and enhanced rtc?

Do I want or need HPET if I have rtc?

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## completemongerel

hey, using rtc you'll get the annoying;

"Cannot access the Hardware Clock via any known method." and your clock will always be wrong  :Sad: 

e-rtc 

simplistically, e-rtc gives you access to bios clock and rtc is for a different (external rtc?) use. 

as for hpet, do you need an hpet? i have never had it enabled. i dunno really what it does maybe someone can enlighten us.

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## audiodef

I have a Gentoo audio production machine. I'm going to test e-rtc. HPET - or some kind of timer, anyway - is needed for sequencing. I was wondering if HPET would be redundant for audio and music sequencing if you already have an rtc. 

My clock has never been wrong using rtc, but I'm looking forward to see what e-rtc does!

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## completemongerel

 *Quote:*   

> My clock has never been wrong using rtc

 

oh okay, whenever i've used rtc i get the aforementioned error. but whatever works is good. if you could post re the hpet i'd be interested how it all goes.

i read somewhere that e-rtc is needed for such things as chrony (similiar to ntpd) so i guess and i mean guess... that the features of e-rtc is needed for some progs and not others which again i guess is where rtc comes in. and again i guess the e-rtc does everything that rtc does + more. logical really seeing as you can't select both at once in the kernel.

good luck.

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## audiodef

I think I need HPET for sequencing. But anyway, I've been running with e-rtc, and it seems to be working fine for audio production. Thanks for the suggestion! I should ping the pro-audio group and ask them if the new standard should be to use e-rtc instead of the old rtc.

----------

