XPS 8940, Better 3rd party cooler

@txhillcountry 

I used m3 x 16mm and they worked perfectly. Other than that, it fit with no problem using the supplied brackets and the black spacers with the NH-D9L

@edob7368 Unless you break something, changing the cooler shouldn't affect your warranty. The warranty does not prevent you from opening the computer case. There are no stickers/seals on the default cooler screws or power connector. You can take the default cooler out and then put it back if needed without anyone being able to tell that you ever removed it. (unless you manage to damage a screw head or something  ). 

Just be careful to clean up the old thermal paste, put the appropriate amount of new paste, gently tighten the new cooler screws as instructed (there are numbers on the board and a pattern on how to alternate tightening so that you balance the tension), and to generally not drop stuff or hit or scratch the motherboard or the tiny components on it with your tools. As long as you take your time and pay attention, you should be done in 10 minutes. 

This just cross my mind after reading so many pages on this topic. Should I be worried that these cooling mods will break warranty?

@txhillcountry I used M3 x 20mm screws and they worked perfect!

Anything longer than 20mm I can't speak to whether they bottom out in the case mounts.

@bertro514 very interesting read on editing the BIOS - thank you for that! I'm not as much interested in the overclocking as I am another topic - is there any chance that the startup fan BIOS errors common on these Dell prebuilt machines when swapping fans can be worked around or disabled through this BIOS edit method?

I'm going to dig deeper into this this weekend, but I thought I'd ask someone who has at least edited a dell bios in the meantime.

@purpledrillmonkey It is possible that a variable could be tweaked to disable those fan alerts, but I have no idea what that would be and I recommend not editing anything unless you read from several reliable sources that it works. You don't want to edit the wrong address by mistake and make your machine unbootable. (that can be reverted with a hardware EPROM flasher, but it's a bunch of trouble).

From what I've read, newer versions of the BIOS fix the fan issue. My G5 never threw that error and my understanding is that this is due to the newer BIOS they put on my machine. There might be a similar update for the XPS. I would look into that first before poking around BIOS code.

Throttlestop improved my cinebench by 50(!) points with no change in temperatures at all (Vetroo V5 kept things at 70C or less).

@txhillcountry - I have installed the NH-U9S using m3x25 set screws (grub screws) ,,, I think it would work for the NH-D9L also. This way you can still maintain the design intent and appearance of the Noctua mounting by still using the included thumbscrews. Here's a link to my post regarding this if you are interested.

Replying to myself to note that my throttlestop gave me an extra 500(!) not 50 points.

@SomeCaliGuy nice!!! I had to do a double-take when I read "50", but then I saw your reply. That's more like it! 

@SomeCaliGuy - notes to self are always a good thing !!

Thanks a lot for all your tips. Just got my new 8940 with the new I7-11700 and can confirm that everything already mentioned here applies to this new processor as well.

Overclocking:
A special thanks to @bertro514 , undervolting worked great and removing the turbo boost drastically increased performance: Seems like -100mV on the CPU Core seems to be the max for the i7 - Anything below caused instability.

Cooling:
- The Arctic i13 X CO fits without any modifications. Just remove the stock cooler, unscrew the screws from the motherboard and screw in the ones included in the Arctic. Thermal paste is already applied on the new cooler. Removing the old thermal paste using rubbing alcohol worked well.
- I have also replaced the case fan with an Arctic F9 PWM PST CO and attached another one of the same type fan to the front side of the case (the PST means a splitter is attached to the cable -> no additional cabling needed to run the second fan).
Nice to know: The original case fan was mounted using rubber insulators. As you can screw in the F9 with the screws included in the pack, you can go ahead and use the rubber insulators the old fan was mounted with to get the new fan in the front to stick to the case. 

Temps:
After replacing the stock CPU and case fan, and adding an additional fan to the front of the case, temps dropped to around 58C on average running Cinebench. Multi-Core Score: ~11150
After undervolting and increasing the boost time to infinite, temps increased to 69-70C running Cinebench, whilst performance increased significantly. Multi-Core Score: ~14050. Idle temp: ~29C 

Cost:
2x Arctic F9 PWM PST CO 2 x 5.50€
1x Arctic i13 X CO 26€
-> 37€
- Nothing else needed -

@NHRP , so glad to hear it worked well for you. That's a great CB score, and the temps sounds very good! 

In my tests with undervolting, I noticed that CPU cache is way more sensitive and prone to freezing and crashing. In my tests, I could take core close to -150 and it would be stable, but lowering cache voltage beyond -20, -25 started freezing when I left the computer on idle for longer periods. 

Oh wow, -150 is a lot!

I've kept my cache voltage at -20 like you suggested (which works great). Haven't done any further tests on that one to be honest though 

@bertro514 yeah I've had no fan issues with the XPS 8940 - I was actually thinking of trying it with the Alienware R11.

Most PWM fans seem to not spin up on boot on the R11 and the BIOS reads this as an error on the R11 since there's no tach signal.