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13th November 2013, 09:11 AM   |  #854  
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Originally Posted by ogboot

I gave up on UV my processor for the time being. First I tried global -50, then -25, and finally -12.5 but only at 300mhz. Eventually locked up & rebooted on each setting. PVS4. 002 kernel is super smooth & stable for me at stock voltage.

Sent from my Nexus 5 using XDA Premium 4 mobile app

Geek Talk Below:

CPU Binning and Undervolt relations: (example voltage based on Snapdragon 800 aka MSM8974).

For MSM8974, there are total of 8* binnings (the best one pvs 7 uses the same voltage table as pvs 6, Qualcomm hasn't assigned its own unique voltage table yet, they do this often then later on they assigned a unique table for it after stability testings' completed)

Ranging from 0 to 7. 0 requires the MOST/HIGHEST voltage range to boot, and 7 required the LEAST/LOWEST voltage range to boot.

Because lower binning SOCs use higher voltage values, they tend to run hotter than higher binning versions.

So how do these different binnings factor when undervolting?

Often time you will see some users claiming to have HUGE undervolting values such as -100mv, -125mv running completely stable and yet some users can barely undervolt -50mv before running into stability problems. So why such discrepancy? CPU binning is part of the variable in this discrepancy.

users with CPU
Binning 0 running @ 2.3 GHz is using 1.100 volts
Binning 1 running @ 2.3 GHz is using 1.075 volts
Binning 6 running @ 2.3 GHz is using 0.95 volts

so if you take binning 6 compare to binning 0, you are "effectively" pre-undervolted from the factory by 150mv ALREADY! Wow... So users with binning 0's MASSIVE -150mv undervolt compare to binning 6's STOCK voltage is effectively the SAME!

Wait a second... Isn't Binning 0 designed to run @ higher voltage? SO the massive undervoltage should crash correct?
Answer: Yes and No...

Lower Binning SOCs may need higher voltage to BOOT, but when running, it may use the same nominal voltage as the higher binning SOCs. So once successfully booted, you can run the lower binning SOCs at lower voltage values than during boot.

Hm... So when is Undervoltage applied? When using my FauxClock, the voltage is applied after Android successfully finished its initializations (by this time, the kernel has LONG initialized all the peripherals and system is already in a good running state with Power Management running and initialized).

This only explains PORTION of the mystery surrounding undervolting. The remaining factor depends on the Quality of the SOC you were given when you bought your phone. It's really based on chance and as many of you already know if you followed my kernel development through all theses years, my famous quote of "NOT ALL CHIPS ARE CREATED EQUAL" remain true today and in the future.

Also when you post your undervoltage value, to make it more useful, make sure you post your SOC binnings as well
Last edited by faux123; 13th November 2013 at 09:13 AM.
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