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Overclocking and black screens when attempting to unlock: Explanation & Solutions

I wanted to explain black screen issue many folks are encountering with overclocked kernels. The root cause is that voltages at higher clock speeds are not high enough to get the screen to turn on. In other words, if your screen is off and your phone scales beyond 800Mhz, the phone does not have enough power to turn the screen on. You'll almost always scale to the max the moment you hit that power button.
There are a few ways to prevent this from happening (from best to worst):
Create a "screen off" profile in SetCPU to restrict the clock to 800Mhz or below when the screen is off. I think it's obvious why this works. At the same time, a lot of people already do this, which explains why everyone hasn't been having the problem.
Use the conservative governor. Because it scales more gradually, it won't immediately jump past 800Mhz when you attempt to power the screen. There is still a chance of encountering the issue if you attempt to turn on the screen if the device has been busy for a while.
Increase voltages in the kernel. I started experimenting with this before I decided to come here and recommend the first two options. To get the screen to reliably turn on at higher clock speeds, we'd have to raise the voltages substantially. So we'd end up with more risk of damaging components, degraded battery performance and so on. Once the screen is on, the cpu does not actually need more power than it's being given in today's frequency tables. Thus, we'd effectively be increasing power consumption all the time to deal with a need for more power at screen on. Clearly a bad idea.
Unless you're using SetCPU profiles (or equivalent) or the conservative frequency governor, you're going to get black screens. Cyanogen, Pershoot, Evil's and my kernels all use roughly the same voltages, so you're going to need to apply this solution regardless.
There you have it.

*Applauds*
I bow down to your wisdom, sir!

Can you explain why this doesn't happen to me when I'm on CM 6.1.1 ROM?
With setcpu settings at 1209/368 (ondemand scaling, no profiles) I have black screens on Virtuous but neveron Cyanogen's mods.

rgl12miami said:
Can you explain why this doesn't happens to me when I'm on CM 6.1.1 ROM?
With setcpu settings at 1200/300 I have black screens on Virtuous but never
on Cyanogen's mods.
Click to expand...
Click to collapse
I'd have to do more testing to confirm but I would guess more load is generated (events triggered) with Sense ROMs at the time of wake, causing the ondemand governor to scale up to nearly max more rapidly than CM.
There's a simple way to see if it'll ever happen on CM. Set your governor to "performance", with clock speed above 1Ghz. Turn off the screen and see if it fails to turn after a few attempts at toggling it on and off.

I did what you suggested about 30 times and no one has failed. It's a shame,
because I do really love your ROM: speed is incredible. But what bothers me
the most is when the alarm sounds or I receive a call and the screen refuse to
lighten up. I will keep an eye on your rom and for sure I will be back on it soon.
Great job! The best sense rom i've ever seen.

Thanks for this. Works perfectly on my Stock SenseUI ROM with virtuous kernel

Thanks! That explains why the issue hasn't been happening since I set my profile to conservative. That was probably the most annoying issue since I got my G2.

I bet the fact that every cpu is different would also explain why it happens to some and not others.
Again every cpu is different, but here is my settings for screen off. Min 245 max 245. I started min 245 max 368, dropped max down and no adverse effects and great bat life. I have no blackscreen/wakeup issuses. I've been using setcpu to save battery since before the first oc module/kernel.
Would def test kernel that drops below 245 and/or uv it greatly.

fastludeh22 said:
I bet the fact that every cpu is different would also explain why it happens to some and not others.
Again every cpu is different, but here is my settings for screen off. Min 245 max 245. I started min 245 max 368, dropped max down and no adverse effects and great bat life. I have no blackscreen/wakeup issuses. I've been using setcpu to save battery since before the first oc module/kernel.
Would def test kernel that drops below 245 and/or uv it greatly.
Click to expand...
Click to collapse
What do you mean that every CPU is different? At the hardware, firmware, software level?

gee one said:
What do you mean that every CPU is different? At the hardware, firmware, software level?
Click to expand...
Click to collapse
I think he means every cpu handle overclocking differently, for example ive been very unlucky and my cpu cant handle anything above 1.1 Ghz and it crashes if i set it up any higher but lots of people running theirs at 1.8 and they are stable
its just like overclocking PCs every cpu handle overclocking differently even if they have the exact same spec.

I'm bumping this due to how useful this information is and how often the issue still comes up.
Sent from my HTC Vision using XDA App

rmk40 said:
I wanted to explain black screen issue many folks are encountering with overclocked kernels. The root cause is that voltages at higher clock speeds are not high enough to get the screen to turn on. In other words, if your screen is off and your phone scales beyond 800Mhz, the phone does not have enough power to turn the screen on. You'll almost always scale to the max the moment you hit that power button.
Click to expand...
Click to collapse
I don't understand why I don't encounter this issue at all with AOSP ROMs. Is there an obvious reason I'm missing?

poochie2 said:
I don't understand why I don't encounter this issue at all with AOSP ROMs. Is there an obvious reason I'm missing?
Click to expand...
Click to collapse
This was the first question asked (see the fourth post). Here's the OP's theory...
rmk40 said:
I'd have to do more testing to confirm but I would guess more load is generated (events triggered) with Sense ROMs at the time of wake, causing the ondemand governor to scale up to nearly max more rapidly than CM.
Click to expand...
Click to collapse
I haven't seen this issue before either.

ianmcquinn said:
This was the first question asked (see the fourth post).
Click to expand...
Click to collapse
My bad, I missed that.

Random lockups

As per the title, I have started experiencing random system lockups since yesterday. I have had to perform two battery pulls and I'm starting to worry that my ext partition won't be so lucky next time...
I have no idea what is causing the lockups, though both have occurred while using Swype. Coincidence?
For now I'm going to set my system clock back to 600Mhz and use the default input method for a while and see if I still get lockups, at which point I will probably flash another ROM unless I can find a solution, which is where you guys (hopefully) come in. Is there anything else I can do to diagnose and/or solve the problem?
- Typed from my rooted HTC Legend -

It's most likely the OC that's causing the problem, Swpye shouldn't affect the stability. Unless it's a cracked version

Try interactive governor or flash latest kernel from the other thread.

TheGrammarFreak said:
It's most likely the OC that's causing the problem, Swpye shouldn't affect the stability. Unless it's a cracked version
Click to expand...
Click to collapse
That's peculiar, as I've had the processor on 768Mhz for a while now and I've had no problems at all before now.
As for Swype... it could be. ;P
BlaY0 said:
Try interactive governor or flash latest kernel from the other thread.
Click to expand...
Click to collapse
I'll try that, but what exactly does each governor do?

segphault said:
I'll try that, but what exactly does each governor do?
Click to expand...
Click to collapse
It manages when the processor speeds up. It doesn;t run at 768MHz all the time, that's just the highest you allow. Ondemand scales the frequency up when it's needed, and lowers it again afterward. It seems to be a little bugged in our kernels though, and causes crashes.
Interactive does a similar thing, but without polling the CPU. It also ramps the frequency up a little more quickly. I use it, it makes the phone more responsive (IMO), and also eliminates the need for profiles in setCPU (to a degree)

Just checked my kernel version - I already have the latest version (2.6.32.17). I've also set the governor to interactive as suggested, but I have pushed the max clock back to 768Mhz and the min clock to 122Mhz.
While we're here, is there any way to push the min clock down even lower, or would that require fiddling with the kernel? In which case, I have two questions:
1. blay0, I've heard people who can push their min clock down to something ridiculous like 19Mhz if I recall correctly, which makes battery life last a crazy amount of time. Could you include that as the minimum clock in the next kernel for b 0.8?
2. If not, how do I go about changing it myself?
I want to learn.

segphault said:
Just checked my kernel version - I already have the latest version (2.6.32.17). I've also set the governor to interactive as suggested, but I have pushed the max clock back to 768Mhz and the min clock to 122Mhz.
While we're here, is there any way to push the min clock down even lower, or would that require fiddling with the kernel? In which case, I have two questions:
1. blay0, I've heard people who can push their min clock down to something ridiculous like 19Mhz if I recall correctly, which makes battery life last a crazy amount of time. Could you include that as the minimum clock in the next kernel for b 0.8?
2. If not, how do I go about changing it myself?
I want to learn.
Click to expand...
Click to collapse
You'd have to mess around with kernel source code. I wouldn't know where to begin, sorry

Wouldn't 19 MHz min also make the phone painfully slow to wake up? Just curious.
Sent from my Legend using XDA App

MaBlo said:
Wouldn't 19 MHz min also make the phone painfully slow to wake up? Just curious.
Sent from my Legend using XDA App
Click to expand...
Click to collapse
That did cross my mind but other users have reported success with it, so I figured I might as well give it some investigation.

I had mine go to 19 min with screen off once, it did my head in. Maybe interactive with a reasonable upper limit with screen off (like 400) would work, who knows

TheGrammarFreak said:
I had mine go to 19 min with screen off once, it did my head in. Maybe interactive with a reasonable upper limit with screen off (like 400) would work, who knows
Click to expand...
Click to collapse
Maybe not quite 19Mhz, then.
Perhaps we should do some testing to see how much processing power is needed to wake the phone quickly? Is there any way to test that?

Back on topic, I just had another lockup while using the interactive governor. This time I froze up while loading Fruit Ninja.
Now I'm at a total loss for what could be causing the lockups.
- Swyped from my rooted HTC Legend -

Seeing as nobody can seem to pin-point the problem, I'm moving to CM7 permanently as soon as it's released as stable.

[Q] Best SetCPU Settings for Wildfire

how to save battery life when using setcpu?
same that:

Firstly, this is the Android Development Section, so, you have posted this in the wrong section.
Anyway, to the topic, I just watched the video. I don't quite get what the problem is. What part of the video are you unable to follow? You can keep it at the same levels depicted in the video, but, a few of my suggestions:
* Min at 691 is too much. Keep min at 245, it will save battery even when screen is on
* Screen off values are too low. In my personal experience, if it is kept so low, the phone hangs when an incoming call arrives. So, after much experimenting, I have seen that keep the min value at 245. Anything below that can hang the phone. (Obviously many people do get it working fine at 160 MHz, but, this is my personal experience with my Wildfire)
As for the settings under the "Advanced" Tab, I am not having that many settings in my version of SetCPU, so cant really comment on that.

3xeno said:
Firstly, this is the Android Development Section, so, you have posted this in the wrong section.
Anyway, to the topic, I just watched the video. I don't quite get what the problem is. What part of the video are you unable to follow? You can keep it at the same levels depicted in the video, but, a few of my suggestions:
* Min at 691 is too much. Keep min at 245, it will save battery even when screen is on
* Screen off values are too low. In my personal experience, if it is kept so low, the phone hangs when an incoming call arrives. So, after much experimenting, I have seen that keep the min value at 245. Anything below that can hang the phone. (Obviously many people do get it working fine at 160 MHz, but, this is my personal experience with my Wildfire)
As for the settings under the "Advanced" Tab, I am not having that many settings in my version of SetCPU, so cant really comment on that.
Click to expand...
Click to collapse
Should it be scaling on ondemand?

CEBZ said:
Should it be scaling on ondemand?
Click to expand...
Click to collapse
i use ondemand and it works well for me

my settings are 652 max 245 min on performance, not one freeze and getting 2 days plus from a charge
screen off profile set at 245max 245min

ephbee said:
my settings are 652 max 245 min on performance, not one freeze and getting 2 days plus from a charge
screen off profile set at 245max 245min
Click to expand...
Click to collapse
what is the scaling u use in screen off ??

ephbee said:
my settings are 652 max 245 min on performance, not one freeze and getting 2 days plus from a charge
screen off profile set at 245max 245min
Click to expand...
Click to collapse
I'm quite rookie on this with cpu and stuff. But, I've read somewhere that the "perfomance" makes that its always running on the max Mhz. So whats the point of having the min on 245 then?
I'm just asking to learn =)

CEBZ said:
I'm quite rookie on this with cpu and stuff. But, I've read somewhere that the "perfomance" makes that its always running on the max Mhz. So whats the point of having the min on 245 then?
I'm just asking to learn =)
Click to expand...
Click to collapse
As far as I know you're correct and performance will simply cause the cpu to run at the max speed, the same as setting min and max the same (except its meant to be slightly better than that as it doesn't bother spending cpu cycles figuring out if it should drop the cpu speed to the min)

SetCPU app and it's effectiveness? Syndicate Frozen ROM

Hey there, I just a few days ago rooted and flashed the Syndicate Frozen rom and am not getting such good battery life...
I was wondering how big of a difference SetCpu makes on battery life/performance in general? With moderate/heavy use (internet browsing, facebook, email, txt messaging) how much should it improve battery life? am getting around 10hours at the moment with moderately light use... Is there any free alternative app that runs comparatively well?
I guess what I'm really asking is: is it worth it to buy setcpu, and will it make a dramatic difference on my battery life? This Rom is supposed to improve battery life, and I think I read is overclocked to 1.2... Will setcpu let me set this underclocked to 1,0 and then like 800 with screen off, 600 idle? Am new to the android thing [have had my EPIC only around 2 weeks today]
Thanks for any help!

Overclock widget does pretty much the same thing, and you're going to want to set something like
20mhz min 1 or 1.2ghz max
Then 100mhz min 400mhz max for screen off.

You can set the speed to.anything you want. If you want battery to be the best then.set it to 100/1000 on demand. If you emwant performance then 100/1200. Also I don't set profiles cause I was reading somewhere that they aren't good to use on any galaxy phone.
Sent From My Evo Killer!

http://www.setcpu.com/
Nice info read up on it and yes you can set it anyway you want like stated above. I bought mine from the market to support the dev for the hard work involved in making setcpu, dont know if you know but it is free for xda members just search for setcpu. It is only $2.00 well worth the price so please support the dev if you can.

063_XOBX said:
Overclock widget does pretty much the same thing, and you're going to want to set something like
20mhz min 1 or 1.2ghz max
Then 100mhz min 400mhz max for screen off.
Click to expand...
Click to collapse
20Mhz would freeze the phone. :O
I personally like running it @ 100 Mhz when screen is off and 1Ghz when screen is on.

Overstew said:
20Mhz would freeze the phone. :O.......
Click to expand...
Click to collapse
I am pretty sure XOBX meant 200, cause your right 20 is pretty much crawling...

Yep, I meant 200, the damn autocorrect kept changing mhz to Hz and I must've clicked backspace one too many times.

Thanks, so it would make a big difference in battery life?
Sent from my EPIC 4G FROZEN and Syndicated

androikid said:
Thanks, so it would make a big difference in battery life?
Sent from my EPIC 4G FROZEN and Syndicated
Click to expand...
Click to collapse
Don't expect it to magically give you another 4 hours up time. 1 extra hour would be high hopes.

I use SetCPU with the CPU set to 200/1000 and ondemand, and the battery life has improved GREATLY, well worth the $2 to support the Dev, IMO, even though XDA members get it free.

I've abandoned SetCPU and uninstalled it. Unnecessary consumption of system resources.
Same with any other user-space app/widget to control CPU speed scaling.
In the Bonsai ROM, the exact same capability, sans the profiles which I (and most people) don't use anyway, can be achieved by setting clock range and governor in /etc/init.d/24-cpufreq script. I expect that all the other OC kernels, if not every custom kernel, has a similar way to set CPU clock governor.

I have mine set to 100/1200 on demand, and it works well for the demands I put on it. Way low consumption at idle, but when I need something it instantly responds.
I routinely get 16-18 hours off the charger, and put it back on the charger with sometimes as much as 40% remaining, but as always YMMV. A lot of it has to do with the ROM, but I'd say that CPU scaling has realized a tangible gain for me.

dwallersv said:
I've abandoned SetCPU and uninstalled it. Unnecessary consumption of system resources.
Same with any other user-space app/widget to control CPU speed scaling.
In the Bonsai ROM, the exact same capability, sans the profiles which I (and most people) don't use anyway, can be achieved by setting clock range and governor in /etc/init.d/24-cpufreq script. I expect that all the other OC kernels, if not every custom kernel, has a similar way to set CPU clock governor.
Click to expand...
Click to collapse
Talking about Bonsai ROM tweaks on a Syndicate thread would be like me talking about BMW mods on a Honda forum. Either way, I looked around in the system folders and I can't find the 24-cpu file you're talking about. I upgraded yestereday from the 2.1 SyndicateROM to this, and for the first few hours, the ROM itself was definately quicker...I don't know if that's just because I came from 2.1 to 2.2, not to mention all the other 2.2 tweaks. After a few hours, I completely forgot that I could overclock this to 1.2Ghz. Installing SetCPU and bumping it to 1.2Ghz felt like just another jump. System resource consumption aside, it makes the phone all that much quicker while going between screen, apps list, closing apps, etc.
I could care less about battery life because I've learned to always have a charger around me since my days of the Moment, of hell, even my Treo's. I want fast, SetCPU is something I can see the difference in just from turning it on and off and seeing the differences.

[Q] [HELP] Setcpu Advice.

Using Kyrillos v6.0 OC.
I am experiencing a rather greater battery drain almost 1% for every 5 minutes as compared to Non OC version.
A new found love for games i want to stick to the OC version. Please let me know the Setcpu settings and profiles i can use for a better battery without letting down on the performance.
It took me a great while to unfreeze my phone. Turned out the phone freezes at 1300 original setting.
Thanks In Advance

Try a lower value. eg @1120MHz

Try lowering the MHz a bit or even better, try lowering the voltage for different frequencies. But in general, a phone at 800mhz+ is going to drain fast no matter what.

use this settings
use setcpu or nofrills with the following settings
max-1000 mhz
min-100mhz
gavernor-conservative

thanks for the info

kyrillos13 said:
Try a lower value. eg @1120MHz
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Click to collapse
@Kyrillos13 : And the minimum value ?