Why is the XPS 9550 POST speed so slow. The amount of time it takes from when you press the power button to when it starts Windows is about 5-7 seconds. This slows the startup time of the laptop significantly! With an SSD a cheaper Acer computer beats this computer to POST by about 3-5 seconds. It takes the Acer about 2 seconds to start booting Windows. I am on the latest BIOS/UEFI as of 24/04/2016 which is 01.02.00. I suspect this could be something to do with fast booting! Please fix this as it would be amazing to have a faster booting computer!
The XPS 13 and Macbook Pro 15 both have DDR3 memory. The XPS 15 uses DDR4 which performs memory training as the bios initializes. It will always have slightly longer boot times vs DDR3.
My additional research: According to Anandtech "The downside to the user is that the number of modules in the system effects the boot time of the device. A fully laden quad-channel Haswell-E system adds another 5-8 seconds to perform this procedure, and it is something that cannot be circumvented through a different routine without disregarding part of the specifications."