USB Boot drive or Boot DVD don't show up on Mac Pro

[sebh]

Hi,

i update my Mac Pro 2010 from 10.10.3 to 10.10.4 after restart it dosn't boot anymore into osx it just restart after a while. So i want to boot from a USB Boot drive with 10.10.4 on it. But the Drive dosn't show up when i hold alt at start up. The same when i try it with a boot dvd. i have also tried the Drive with my Mac Book Pro Retina there it was no Problem to Boot with the USB Stick.
I did a PRAM resett but same result no USB Boot Drive.
Now i don't know what i can do to reinstall OSX or repair it.

 

[h9826790]

Remove all HDD and try again? Of course just for testing purpose.

Also, did you connect the USB drive to the native USB port?

Did you use the internal SuperDrive to read the DVD?

 

[h9826790]

The recovery partition doesn't work as well?

 

[sebh]

The recovery partition doesn't work as well?

no recovery partition that's why i have to do it with usb.
yeah i tried all usb ports and for the dvd the internal drive.

 

[h9826790]

Just to confirm that you still get the boot manager by holding "option" during boot, but just no selection for the DVD or USB drive?

Hold "C" during boot also doing nothing?

 

[sebh]

Just to confirm that you still get the boot manager by holding "option" during boot, but just no selection for the DVD or USB drive?

Hold "C" during boot also doing nothing?

boot manager is there.
i haven't tried holding c i give it a try later.