XPS 8940, add 2nd 3.5" HDD

@XPSUser123ABC  CD, DVD and BluRay drives are all types of optical drive.

1. There is a second 3.5" drive cage below the CD/DVD/BluRay drive in the XPS 8940.
2. The heat problems being encountered by users of the XPS 8940 with non-K processors is due to the inadequacy of the CPU cooler specifically and the case cooling generally.
3. Yes.
4. There is a spare SATA cable, which is located by the 2.5" drive cage, ditto power cable.
5. Yes.

That is helpful in clarifying what you wrote.  Hope you don't mind, I have a couple of follow-up questions.

1)  I will look for the second 3.5" cage below the CD/DVD drive. 

2)  I will assume by your answer that the XPS 8940 has a NON-K processor? I have the (Intel(R) Core(TM) i7-10700 CPU @ 2.90GHz).  I Googled NON-K and it is a locked processor.  K is for unlocked.  

If I left everything as is (512gb SSD) and 2TB 3.5" SATA HDD, is there still a cooling issue?  If I switch out the current 2TB and replace it with a 4TB or 6TB SATA 3.5" HDD, how much more of a heat issue can I expect to encounter?  Thanks.

1. Yes.
2. The -K processors have a tower cooler, whilst the non-K processors have an under-sized pancake cooler.

The cooling issue is more about what you do with your PC.  What will you be using it for?  If you play games at high frame rates in high resolution, do video editing or large 3D rendering, then you will probably see the CPU thermally throttle due to insufficient cooling, reaching 100°C.  If you only send emails or have a few tabs open in a browser, then you'll probably be fine.

Thanks again.  Very helpful.  I use the XPS mainly for the web (Youtube, Podcasts, etc.). I don't play any games (I never had a fast enough computer to do that).  I use Photoshop and plan to get into video editing.  Just general stuff like editing family videos.  Process the odd GoPro video.  

So, for the above, I may not have to worry about overheating?  Adding an extra HDD will not increase the heat inside the case of the XPS 8940 requiring a larger fan? 

What is the simplest thing I can do to help with the heat, get a larger fan inside the computer or get a bigger heat sink?  If bigger heat sink, would it be easy to install for the i7? 

@XPSUser123ABC  You may not have too many problems, then.  The additional HDD shouldn't add too much to the overall heat burden.

The main item that would require changing if you did start to experience heat issues is the cooler on the CPU.  This thread shows what others have done and are doing.

Thanks.  You have been very helpful.  I will order my HDD soon. 

Thank you for the examples. What right angle cable did you find  ?

Thanks for your valuable information. Please tell me what kind of hard drive tray you use to mount the 3.5" HDD to the top bay under the optical drive. Any Dell part number I should know.

WD Black is 10,000 RPM and they get VERY HOT.

Western Digital blue, the warranty is 2 years.

Western Digital black the warranty is 5 years. 

Western Digital red & purple the warranty is 3 years. 

There are two 3.5 cages.  They both work fine, I use them both.

My system does not have any SATA power cable to start with. Can you show me where your SATA power comes from? Is it from the motherboard? Please show me the connector and the cable. I need to order this cable to add my first hard drive/DVD to my XPS8940. Thanks for your information.

If you check the service manual pg 55, component #14 is the plug marked SATA PWR. You need a cable to get power 3 connectors to hard drives and 1 power connector to DVD. Dell P/N: 0N4XMK. I bought it from eBay for $4. Dell gave me a quote on the same part:ASSY,CBL,3,5HDD,PWA,G5 $5.99.

eBay has more compatible cable (for Optiplex 7040 part 07G26H - search for it).

My XPS 8940 now has 2 10TB WD red hard drives.

Good luck.

Did you have to buy any screws or was it just take out plug in and play? Was thinking about doing the same to clear the perforations on the front side for better cooling.

So just checking, you just plugged them into the available SATA and power cables already in the box, fired it up with no BIOS modifications, and MS's Disk Management module recognized them? I tried adding a 4TB WD red pro and neither the bios nor MS/DM detected it. I'm sending the drive back for a replacement, but just thought I'd ask in case there was a special nuance that bypassed me. Thanks, GB