I have a Dell M4800 with a Core i7 4900MQ, however I cannot get it to run above 800MHz - even on Prime95. I have tried enabling the high performance power plan but to no avail. CoreTemp is not reporting high temperatures so that is not the issue.
Also the GPU *may* be running at 405MHz when it should be at 666MHz, although I've had conflicting readouts from different programs on that. Again, no high temps.
Does anyone know what the problem might be here?
Does the system correctly identify the AC adapter, or does it show "unknown" in setup (F2 at powerup)?
If the AC adapter is not correctly identified (or is a non-Dell third party adapter), the system will run as if on battery all the time -- keeping the CPU speed exactly as you see it.
What operating system is installed? If you haven't already, I would suggest flashing the BIOS:
I would then try disabling C-States and SpeedStep in the BIOS/setup. If it's still the same, what happens if you try a clean boot?
Let us know how you get on.
Thanks for the reply. It's running Windows 10. I have updated to the latest BIOS but that didn't fix it.
I tried disabling SpeedStep and C-States, and that unlocked more mutipliers, although it didn't seem to want to run above x29. I then tried just with SpeedStep disabled and it was running up to an x38 multiplier (the true maximum). In both cases, with Prime95 running, the CPU strangely dropped down to an x23 multiplier.
I don't really want to run it like this though as the drain on the battery will be much higher. What can I try to get it running with the full range of multipliers?
Enable SpeedStep again, then boot to Windows and open MSCONFIG.
Select "boot" > "advanced options" then check the "number of processors" box and select the maximum number of CPUs.
Hopefully that should do it for you.
This solution partially worked but not entirely - now when it is running on battery it has access to higher multipliers, but as soon as I plug in the charger, it goes back down to 8x and will not budge from there.
Given the last description, first try a new OEM Dell adapter -- 130W for integrated video or 240W for discrete. If that doesn't solve the problem, replace the DC power jack. If that doesn't solve it, the issue is with the mainboard -- which is expensive to replace, but likely the only solution to the problem.