XPS 8940, i9-10900 CPU upgrade question

@redxps630​ Thank you so much! Is there a worthwhile difference in performance between the 10900 and the 10900k? I work in music production

I doubt it.  10900k is for people who want to overclock cpu to >4-5 GHz to beat the record in gaming.  If you are not into fast video apps I do not think you need the k cpu. https://www.tomshardware.com/reviews/intel-core-i9-10900k-cpu-review/7

@redxps630​ Thank you!

What are your question on psu? 

@redxps630​ The 500W PSU that came with my XPS 8940 emits a lot of EMI and I would like to swap it for a higher quality PSU. I understand an adapter cable is needed and that the PSU might not fit in the case. Is it safe to run a PSU outside the computer chassis? Is the adapter cable sure to work?

You can get a high quality SFX psu which can sit loosely inside 8940 case.  Psu outside case is not shielded by metal case therefore emits more EMI than you want.  It is a desperate move for people who want to power high power gpu. Adapter cable from moddiy made of premium quality materials is better than generic ones.

@redxps630​ Thank you, could you please recommend a PSU that will sit inside the case and emit very little EMI?

Also, is this the cable I need to get? Main Power 24 Pin to 6 Pin Adapter Cable for Dell OptiPlex 3040 3050 3060 - MODDIY

I am not familiar with lowest EMI psu, but you could try put the pc in a separate room or basement then use Sunshine and Moonlight app to view display monitor in your music studio.  distance is the best EMI reduction

https://www.youtube.com/watch?v=TQwCJYiLqSo

Sunshine: https://github.com/LizardByte/Sunshine Moonlight: https://moonlight-stream.org/

Since you did not mention K level SKU. 

• 40% faster CPU speed
• 10 x 2.8 GHz vs 8 x 2.5 GHz
• 4 threads more CPU threads
• 20 threads vs 16 threads
• 0.5 MB bigger L2 cache
• 2.5 MB vs 2 MB
• 4 MB bigger L3 cache
  20 MB vs 16 MB
• 128 KB bigger L1 cache
  640 KB vs 512 KB

That is just the NON K  differences.  You would be giving up 4 more cores some cache , and a higher base frequency for more heat and no real gain. 

K versions the 10900k has a base clock of 3.8Ghz  vs 3.5Ghz

Don't bother upgrading from the 10900 to the 11 series, at that point just go with a new platform.  You cannot really adjust the 10 series or even 11 series K CPUs on the 8940. Even if you could you would actually need an 360m AIO to get any real gains as any air cooler is going to instantly throttle. 

@sidewinder88​ You cant the pinout on the dell PSU is  not standard even if you got a 24 pin to dual 4 pin for the PSU,  The pinout doesn't match normal mb standards, your just going to nuke the board in the process. There was one user that claimed they got a non Dell PSU to work, outside of that . I would not trust it.  

Just for clarification the Dell Mb isn't 24 to 6 pin  it is actually.

processor power-cable connector (ATX CPU1) 4 pin 

processor power-cable connector (ATX CPU) 4pin 

Please don't take the bad advise you are just running the risk of frying your pc at worst and frying just the motherboard at best.  You could get away with running 1 4pin to AUX CPU since you have a 10900 series, it needs the extra 4 pin adapter for the higher wattage of the CPU.   

Even standard ATX boards have 24 + 4 and 24 + 4 and + 8 aka dual 4 for higher end CPU's . That is in part because the 24 Pin can only draw 150 watts maximum for the CPU. 

Anyways here is just some info. Take it for what it is worth. 

Re: is this the cable I need to get? Main Power 24 Pin to 6 Pin Adapter Cable for Dell OptiPlex 3040 3050 3060 - MODDIY

Not sure of that cable.   User verified 24 to 6 pin cable for 8940 is in this thread:

User onefunkydude had done it on XPS 8940 using a coolermaster SFX 750w psu and Amazon 24-6 pin adapter, “I used the adapter COMeap 24 Pin to 6 Pin ATX PSU Power Adapter Cable for Dell Motherboard with 6 Pin Port 13.3-inch(34cm) on amazon and it works fine”  

https://www.dell.com/community/XPS-Desktops/XPS-8940-PSU-upgrade-to-850W-that-fits-inside-the-case/td-p/7781721/page/3

@redxps630 one user in all of the dell forums and reddit managed to upgrade the system with an on dell psu,...  Not sure i would be putting this out here as good advice to go and try. As the link you posted even states it is a Dell Custom PSU and the pinouts are non standard.  Yes he posted some pictures, and a google doc with some graphs , but never actually posted pictures of the pc actually booting with that thing installed. 

That is a huge gamble to take with with a computer unless you are willing to loose out on its worth if something goes south.  TBH I don't actually think he ever had it working. But that's just my personal opinion. 

the adapter works with small downside.  Optiplex 7080/5080 use same psu as 8940.  Opti user has also validated that adapter can power up pc. https://www.dell.com/community/en/conversations/optiplex-desktops/24pin-to-6pin-convertor-psu-fan-continues-to-spin-after-shutdown-opti-5080/668ff8ea45b2fb6eebfb91aa

@redxps630​ I can say I validated it and it works great, without proof of the system booting. I would take it with a grain of salt. I am not trying to be a negative nancy. there is a whole reddit and pages and pages of people on here dedicated to upgrading the 8940, tbh its almost become a tinker machine vs an actual pc.   Point is no one else has even tried this to validate it. You would think there would at least be one more.  

I am just erroring on the side of caution, that the post is filled with actual info about the psu and that its custom, even reddit supports this.  But one person does it with very little proof other then a picture of a non turned on pc and a doc file.  Honestly you can install up to a rtx 4070 super in this thing which gives you about rtx 3090 performance . You don't even need to change out the psu as it pulls the same wattages as the stock 3060 ti that is installed in the machine.