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80 Posts
0
72492
May 25th, 2015 12:00
CPU stuck at 500 Mhz (slow) when on battery
XPS-13 DE, Ubuntu 14 + kernel 3.19, BIOS A04
Since installing A04 this morning, it hasn't hung sleepinng or waking (yet). Though I'm getting just as many double keyboard hits as I was before.
When waking from sleep, or if booted, when running on battery, the CPU is stuck at 500 Mhz (very slow). Forever. Nothing will make it go faster. When in this condition (whether booted or woken from sleep), while it's slow, if I plug in power, even for a brief few seconds then unplug again, the CPU instantly jumps to 2,000 to 2,600 MHz and stays there. Then when I unplug power, the CPU stays fast.
Again, this is not specific to sleep. Any time the XPS13 is booted or woken from sleep, while running on battery - it's stuck at 500 MHz. The only way to restore its full speed is to plug in power. Once you do this, the XPS13 will run at full speed even if you unplug the power.
Definitely a bug... not sure if it's in the BIOS, Ubuntu, whatever.
Mike A2
39 Posts
0
May 25th, 2015 13:00
Interesting. What tool are you using to check the clock speed? I just applied A04 and am not seeing this particular behavior. According to powertop and /cat/proc/cpuinfo, I'm seeing clock speeds ranging from 500mhz up to 3ghz.
Ubuntu 15.04 running kernel 4.0.4
MRC01
80 Posts
0
May 25th, 2015 13:00
I'm using i7z.
And the speed changes are obvious - it's 5-fold slower or faster when you run anything CPU intensive (like Minecraft).
Both "cat /proc/cpuinfo | grep MHz" and i7z report the same.
Also, when waking from sleep Bluetooth stops working. Nothing short of a reboot will bring it alive again. rfkill block/unblock, using the UI to turn if off then back on, nothing avails.
MRC01
80 Posts
0
May 25th, 2015 17:00
More info: this problem is intermittent.
I just slept it for a couple of hours, then when it woke up, CPU speed is fine.
Problem not solved; it's only intermittent.
dougam
2 Posts
0
July 20th, 2015 14:00
Hi,
Are you using the Dell Power Companion? I just got an i5 version (running Windows) but noticed that if I sleep after using power companion it would wake and get stuck at 500mhz.
If I use the AC adapter directly it will work fine. It is possible you are using power companion or faulty AC adapter
jkudish
4 Posts
0
August 3rd, 2015 11:00
I get the same issue using the power companion. Haven't figured out a good solution yet.
dougam
2 Posts
0
August 5th, 2015 08:00
Dell released a recent BIOS update A05 have you tried that. I returned my power companion so I cannot test.
jkudish
4 Posts
0
August 7th, 2015 23:00
I've been running BIOS A05 and Linux Kernel 4.1.3 for the past day and so far have not been able to reproduce the problem. I'll let y'all know if it comes back again.
chrismiles
3 Posts
0
August 8th, 2015 02:00
Hi, Just wondering if the CPU speed issue was the reason you returned the power companion? I have been considering getting one but have not been able to find reliable customer reviews for it and feel a little nervous about dropping the £100 the UK site is asking for it.
unixfg
1 Message
0
August 20th, 2015 09:00
Just had mine do the same thing you're describing this morning on A05 and kernel 4.1.5
I didn't know what the problem was for a while, but I've been having this problem since I bought it (A02)