I have the same machine and now I'm running Ubuntu 16.04 (downloaded directly from Ubuntu's site). The issue is that I'm not happy at all with this installation. Everything works slowly and I don't know the cause (you can check this thread).
Can you tell me about your experience with 14.04? Also, do you have this boot problem?
My experience is the same. Contrary to what they have advertised, this laptop is not compatible with Ubuntu. 14.04 is even worse. Support for Skylake CPUs does not exist in 14.04's default kernel.
What kind of slowness are you experiencing? GUI? That's because the nVidia M1000M GPU uses the open source Nouveau drivers out of the box. Installing the proprietary driver is also a hit and miss. Most of the time it breaks the system and you cannot even login to X.
In short, this laptop does not worth a penny as a Linux workstation.
I have this laptop (Precision 5510, 32GB RAM, i7-6820HQ) for about one week and all I have done until now are optimizations (Windows/Ubuntu) and still the computer behaves so slow (compared to every laptop I had before). It gives me a pretty bad feeling. For that price I expected that everything to work seamlessly.
The pre-boot time takes 8-10 seconds (and I'm not the only one having this issue. Check here).
Until I get to Windows/Linux I need to wait another 20 seconds.
Every application starts with a small delay (~ 1 sec).
Resizing an application is a slow process.
My BIOS/drivers are up to date.
In Ubuntu (16.04, 64 bits):
- I updated the kernel to 4.7.5-040705 (before that I tried 4.5 and 4.6)
- the Nvidia driver is now on 370.28 version (before that I tried also 361.45, 364.19, 367.44 and 370.28)
In Windows (10 Pro, 64 bits), the same: the latest drivers are installed.
I thought that maybe there is an issue with the SSD and you can read here my question. No answer.
I really don't know what else to do.
Kernel 4.5 and 4.6 are considered deprecated. Use either 4.4 or 4.7.
Your boot time seems normal. If you are concerned about the BIOS boot time (Preboot as you call it) then I'm afraid you aren't the only one. I too find the BIOS boot a little slow. I have informed Dell to do something about it. Having said that there is an option in the BIOS to alter the BIOS delay and another option to set a Minimal hardware check. Once you have the system correctly set up then you can live with the delay.
Under Linux if you can set the system up to use EFI then Linux will reach the Grub screen faster.
As I said, I'm using 4.7.5-040705. The boot process is by far very slow. On my old laptop (L702x, i7, 12 GB RAM, 256 GB SSD) I need to wait ~10 seconds until the Ubuntu (16.04) is up and running.
It's the same situation with me and exactly the same notebook.I buy it in June and still wondering what a sh*t is this ... Also I buyed and dock which never succefully run 2 external monitors! For that amount of money I expect peace of art ,not a some buggy laggy *** !!!
Thank you for posting your settings about Ubuntu.