Q: Mac pro does boot to white screen no chime

Follow these steps:

Restart your Mac with the Shift button pressed.

- Shut down your Mac

- Wait until your computer turns off and after that press the Power button

- Right after you hear the startup tone, press and hold the Shift key

- Release the Shift key when you see a grey Apple sign and the progress bar below this sign

- Once you see Desktop, start a Disk Utility scan to detect and repair file system errors (don't forget to choose your main hard drive)

- Click on Verify Disc and then, if asked to fix problems, on Repair Disk

- After this, click on Verify Disk Permissions and then on Repair Disk Permissions

- After the process is finished, shut down your Mac and turn it back on after about 30 seconds

Apart from that, take a look at this Apple article and follow the instructions on Resetting NVRAM shown there: How to Reset NVRAM on your Mac - Apple Support

Take a look at the steps suggested by Apple in this article:

If your Mac won't turn on - Apple Support

Take a look at this article:

http://www.macworld.co.uk/news/mac/steps-take-when-your-mac-wont-start-3423817/

Hope this helps!

Does the Power light light?'

Do the fan spin?

Do the HD spin?

You can take the side cover off, there is not interlock

Are any lights lit on the logic board?

Try resetting the SMC and NVRAM

Intel-based Macs: Resetting the System Management Controller (SMC)

About NVRAM and PRAM