Not gonna work, unfortunately. Yes socket is the same lga1151, but motherboard chipset in 8900 is intel 100 series, incompatible w intel 8th gen cpu such as 8700. here is Intel official statement  9th and 8th Generation Intel® Core™ Desktop Processors use an LGA1151 socket. However, they require motherboards based on Intel® 300 Series Chipset. Some Intel® 300 Series Chipset based motherboards may need a BIOS update to support 9th Generation Intel® Core™ Desktop Processors. Please check with your motherboard manufacturer for details. These processors aren't backward compatible with motherboards based on Intel® 200 Series Chipset and Intel® 100 Series Chipset.
Hey! I was wondering if it would be possible to upgrade the processor in my XPS 8900 to a i7-8700 since it uses the same socket? I currently have an i7-6700 and would like to give that to a friend for his streams. Thanks in advance!
XPS 8900, upgrade to i7-8700?