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I require help with XTU on Precision M6800 with i7-4900MQ


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Hello everybody,


I'm trying to squeeze some more power from my laptop (Dell Precision M6800 with i7 4900MQ), using XTU, but until now I only got modest improvements.


First of all: this is my first overclocking ever; I proceeded only after I documented myself to understand at least the basics of what I do, but still OC is still a big gray area for me; I wrote on this forum only after I realized that google couldn't provide consistent and comprehensive information, so please I would appreciate helpful replies.


What I did:


-I increased the multiplier with one level (from 38x; 37x; 36x; 36x to 39x; 38x; 37x; 37x)

-I reduced the Core Voltage Offset to -0.100V

-Gradually increased the Core Voltage, but it seems the best performance was when the Core Voltage was left on Default...

*also, any other value of the Core Voltage Offset was only reducing performance.


Obs: My cooling is good, the CPU never goes in thermal throttling. It stays between 70-85 on max load.


So, what I don't understand:


1. why UNDERVOLTING helped and increasing Core Voltage did not much help?

1a. why the "magical" -0.100V undervolting has so big effect and anything else around just ruins things?


2. what is the correct order of altering settings for overclocking?


3. when (and how) the Cache Ratio / Cache Voltage / Cache Voltage Offset should be altered?


4. I am getting a lot of Power Limit throttling, is that normal? (should I aim for a specific graph pattern, what is good and what is not good in how cpu performs?)


* There is a big chance that even my questions are not the right ones to ask, so I pledge to anyone willing to offer some help, if you think I should approach this in a specific manner, I will take any help you can offer.


Many thanks.

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1. Laptop cooling, especially on OEM laptops is barely enough. Undervolting lowers temps so it actually boosts higher.


2. In XTU on 4900mq just max the 4 core ratio then raise bclk if you can. After that mem OC if XTU has the option. On desktop it depends on platform.


3. OC cache as far as possible, you can try adding voltage but if you're thermally limited, which you are, then it may hurt more than help so you may have to try taking voltage.


4. That's because cpu is drawing too much power for it's rated tdp, if you have the option raise max amperage and that may help.

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Unfortunately, the options for my CPU on XTU are rather limited. None on RAM, and on CPU I can only control the following:

-Core Voltage

-Core Voltage Offset

-Turbo Boost Short Power Max

-Turbo Boost Power Max

-Multipliers for all cores


-Processor Cache Ratio

-Cache Voltage

-Cache Voltage Offset


*so, I cannot adjust the current, as the option is not present :(

*also, can't control the reference clock (is locked/greyed)


I replaced the power supply and now I have one that can push up to 330W - I guess this one is for Alienware, of more power hungry laptops. (previously I had the biggest one for Precision M6800, which is only 240W).


Temperature never raised above 86, but now, with current settings I rarely go over 81 degrees (tends to stay around 77-79). I replaced the thermal paste with Coollaboratory metal pads (much safer than liquid metal and totally okay if they touch aluminium, as the metallic foil is indium-based, not gallium).


For now, best position is all cores to 39x, anything higher will only push the frequency up on idle, but drops drastically under load.

Power I put both options to 61W, that covers the power needs of my CPU and leaves some room. The "cruise" drawn power seems to be 47W and for short period it can get up to 58W.


I've been playing with XTU both with Adaptive and Static voltage settings and I could observe that Static doesn't help at all - despite the fact that many overclockers insist on NOT using the dynamic offset and is best to adjust the voltage manually.

When on Static Voltage, overvolting drops performance a lot, for the smallest change, but when undervolting, the performance caps quickly and if I push it more, I only get BSOD


On the other hand, keeping Core Voltage on Default and reducing the offset to -0.100V seems to be the "sweet spot" ... well, I didn't get it right yet, as -0.095V -> -0.100V seems to be the zone that needs further attention.


Despite of many saying the Cache doesn't affect much, in my case, playing with Cache multiplier and voltage offset (i put them as close as VCore settings), seemed to bring some improvement.



I am a bit confused in regard to Benchmark / Stress Tests on XTU... on some settings Benchmarking ends well, with nice score, but then it fails on stress test, other times is quite the opposite... which I don't really understand why would it fail the benchmark, but then do well on longer stress test? Unless, the sudden change between load/idle is the moment when it fails (current drops too abruptly and cpu doesn't recover fast enough?).

Also the marks in XTU don't seem to reflect the actual performance of the machine (computing performance), but rather a combination between computing and power, from what i could see... which doesn't really help me. I need to evaluate the computational efficiency, regardless of how much power it takes.

Some people say that for Haswell Prime95 is not the right stressing tool (can bring accidental overvolting, due to dynamic offset?). What about OCCT, then? Or you would suggest a better alternative? I could just let it render a 3D file, in a CPU-based rendering software...that one keeps all cpus busy full-time.


!! While writing this (nothing else major was running on the machine), I just got a BSOD. I guess it's still a bit undervolted.

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  • 3 weeks later...
Use a 32bit OS for XTU... best scores for Gamer was with a little help from the airco.


I would never run an OCCT or Prime for hours on a laptop, best stress test is daily usage...


WHy XTU 32bit? What's the benefit of it? I am not aiming for the best "score", as I'm not doing it for the billboard. I just want to get the best out this machine, for daily use, as you said it.


I use it for rendering sometimes, when it has to run even 24h sometimes, that's why I left this stressing software to do their thing, to see if it takes the load. Unfortunately, they worked fine, but the "regular" stress triggered the BSOD, which I believe was due to sudden change in power consumption.

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