I thought I'd put this together given the amount of questions and apparent lack of knowledge on what you're getting yourself into with overclocking. While it's a one-click-wonder with SetCPU and JuiceDefender, it's not that simple when it comes to what it's actually doing to the phone.
The first thing you need to know is this:
All devices are not created equal!
Even when they come off the production line together they may not be capable of even getting close to each other with an overclock. This is down to numerous variables, the most important of which is the processor itself. Processors are manufactured in batches from something called a wafer (basically a big chunk of silicon), that batch is then tested to a maximum stable speed and then marketed at a slightly lower speed for the sake of rock solid stability. Dual/multicore processors may have a faulty core disabled and be marketed as something else (hence AMD's Tri-Core processors). This is the reason overclocking works, and the long and the short of it is just because Person A can get 1.3Ghz running stable, doesn't mean Person B can.
So, now we know that whingeing that my Desire can get 1300Mhz but yours crashes every time you go above 1100Mhz is irrelevant, we can move on to the risks. Overclocking is dangerous. That's not an exaggeration, so let me reiterate...
Overclocking is dangerous, You can potentially kill your phone stone dead.
But yet again it's not that simple. Yes, in very rare cases a processor will just go bang and give up, but most of the time other things will happen, behind the scenes, that you won't know about until it's too late.
The basic premise of overclocking is to get a faster processor clock speed. A small jump can probably be attained just by upping the speed itself and be perfectly stable. Going higher is where the problems start. If you start getting crashes/freezes/reboots then the next step is to increase the voltage to the processor to make it more stable, but more voltage means more heat, and excess heat is bad. This can either cook the processor as a whole or a group of transistors. This is more of a problem on a device like the Desire as where do you put the extra cooling?
Another problem is that more voltage can fry an IC track, and/or arc across to a track it shouldn't be on. This could do nothing, but it could also kill a single transistor on the processor or other chips in the device, or maybe multiple transistors and it can also lock them open or closed. This takes us back to random reboots, freezes, and crashes - but this time it can't be fixed.
Then theres a twist. Undervolting can also break things. A transistor is either on or off, and if it doesn't get enough power one of three things can happen - it can work fine, it can not work at all, or it can continually switch until it breaks (what an example? go and flick a light switch on and off until it stops - and it might not be the bulb that goes). If it decides not to work when other parts think it should, guess what happens.
So, bear this in mind when overclocking. If you start getting ANY issues test at stock speed. If you still have issues and/or you kill your phone, it's your own fault.
Mods - I've put this here as it's the place most people seem to ask about OCing, please move it if i'm wrong...
Nicely written and informative. Users must always take their own responsibility when trying to do something "out-of-spec" with their device. I didn't know undervolting could break things though.
It's far far less common and it's not the actual undervolting that causes the issue - it's the power requirements of the device. If you're unfortunate enough to have something keep tripping - it's kind of like when a PSU goes and keeps clicking, there's not quite enough power to flick to On permanently so it just ticks at you till you turn it off or it gives up completely. 9 times out of 10 you'd be fine, but theres always that chance.
Very Nice,
I got a question tough,
I experienced a lot of freezes everytime I flash a AOSP-ROM......
Even if I don't overclock.........I have to pull my battery out every time...
With sense-roms I don't get this problem..........
So my question is, Am I so unlucky that my device just can't handle the different kernels? or am I doing something wrong???
Hope someone can give me a helpfull answer
toosif said:
Very Nice,
I got a question tough,
I experienced a lot of freezes everytime I flash a AOSP-ROM......
Even if I don't overclock.........I have to pull my battery out every time...
With sense-roms I don't get this problem..........
So my question is, Am I so unlucky that my device just can't handle the different kernels? or am I doing something wrong???
Hope someone can give me a helpfull answer
Click to expand...
Click to collapse
My phone freezed several times a day with defrost. But no freez with MIUI/OpenDesire. I dont know why but Defrost §$%#s my phone
toosif said:
Very Nice,
I got a question tough,
I experienced a lot of freezes everytime I flash a AOSP-ROM......
Even if I don't overclock.........I have to pull my battery out every time...
With sense-roms I don't get this problem..........
So my question is, Am I so unlucky that my device just can't handle the different kernels? or am I doing something wrong???
Hope someone can give me a helpfull answer
Click to expand...
Click to collapse
It can be that it is your ext3 partition if you have one...i had a user with freezes...and i did not know what it was...i say him...make all new...he flasht a original rom...root again with unrevoked...flasht my rom again and it was the same...freezes...so he formated the card...and maked a new ext3 and now he have no more problems with freezes
with kind regards..Alex
Good write up. Hopefully people will actually read this and understand the risks before they start pushing zip files with overclocked/undervolted kernels. Personally I've never overclocked any mobile device since I'm not comfortable with the risks that may lead to long term damages.
great job! thumbs up! vote for sticky or linking this in one of the stickys
i'm familiar with overclocking since i've been doing it to my PCs for years. i'm wondering if aosp roms push the phone harder or something than sense based ones?
reason i ask is i've tried a few aosp roms (open desire, defrost etc) and all the various kernels i've tried cause a reboot after a while - 30 mins, upto a few hours. now, i tried richard trips sense kernel and OCd with that no problems at all. very weird
p,s all Ocing was on the relatively small 1113mhz.
Another battery life question - YES I KNOW ---- but i may have i completely wrong in my head how can battery life be so different between different roms using the same or i assume 10.1 software - been on a mission comparing 2 roms, done nothing different to either, same minimal apps very similar usage and same radio latest 11-14-26M or whatever yet one clearly gives a better life [ near double] of the other. Am not saying which as i DONT want a mine is better than yours *****fest, just attempting to get a handle on it.
Jimpy0 said:
Another battery life question - YES I KNOW ---- but i may have i completely wrong in my head how can battery life be so different between different roms using the same or i assume 10.1 software - been on a mission comparing 2 roms, done nothing different to either, same minimal apps very similar usage and same radio latest 11-14-26M or whatever yet one clearly gives a better life [ near double] of the other. Am not saying which as i DONT want a mine is better than yours *****fest, just attempting to get a handle on it.
Click to expand...
Click to collapse
Maybe a diffence in how the kernals handle voltages
tonylee000 said:
Maybe a diffence in how the kernals handle voltages
Click to expand...
Click to collapse
hadnt considered kernal - cheers ------------ more investigating needed
Hi, thanks for reading.
I am a HongKonger. As I know, the global version of M8 is using the snapdragon801AB while Asia version is using the snapdragon801AC. I know the only different of the two cpu is simply overclocking to different frequency. Would the different make development very difficult to support the two at the same time? Or it will just be the same?
I afraid there will be less support for the Asia M8. Will this happen?
I am so sorry that my English is not good enough. Hope you guys could understand what I'm talking about.
Thanks.
CPU Difference
Hi.
I suggest you to be extra cautious about cross-flashing.
S801AB and AC are two different CPU although they are almost identical structure wise speaking.
What might really happen if you cross flash is that ROMs for AB doesn't have a proper CPU scheduler for AC. I am talking about the voltage input for CPU. You might very likely be running AC (0.8V required) with AB's voltage (1.0V). Sure, your CPU can take this little voltage surplus but in the long run this is no different than chronic suicide. The best way to get a proper ROM is to request for one that is made specifically for AC variance. Or, if I had to guess, keeping your stock kernel might do the trick here.
All in all, be very careful.
I have a long time doesn't flash third-party ROMs since One X, and now I got One M8 for a month, everything is great!
That makes me want to try third-party ROM again.
But as I known, lots of ROMs is based on WWE version to develop, and it's use MSM8974AB (2.3GHz)
And...I'm Taiwanese, so obviously my M8 is use MSM8974AC (2.5GHz)
Some information I found, says that these two different model using a different CPU voltage table.
And I don't know I can use these ROMs or not because the kernel is different.
Does anyone using 2.5GHz version M8 and tried the ROMs on this forum?
Yeah, it works fine.
BenPope said:
Yeah, it works fine.
Click to expand...
Click to collapse
Thanks for ur reply, now mt mind is easier now.
But I still get little worry that because voltage table is different.
Is that may cause CPU get problem easier in the future?
I highly doubt the voltage table is not looked up by the cpu type. Do you have any evidence for this?
BenPope said:
I highly doubt the voltage table is not looked up by the cpu type. Do you have any evidence for this?
Click to expand...
Click to collapse
Actually, this information is from Taiwan's forum and that guy who told me this message is a developer, too.
Maybe he checked kernel and sure that voltage table is different.
I am just curious if anyone has tried undervolting yet. I would like to see how much battery life improved and how much heat output can be reduced from SD820.
r u using Stock or CM13, i am not sure if there is any kernel that can support that yet,
Well i will get my phone this Friday. I saw that lots of Roms are cumming out but its my mistake not checking if they have any under-volt support (my mistake sorry). As far as I saw non of the roms support undervolting yet.
It would be very interesting to see how far the phone can be pushed.