My Mac Pro intel based tower starts up but the display dose not show anything.

First, try booting from your OS X installer DVD to see if the problem is still present. If it is, then you probably have an issue with your monitor or your GPU card.

Try this, then:

Boot to the Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

If you have an older MP model, then you should have installer discs that came with it.

No signal to my display from a 2009 Mac Pro. Can't even boot in safe mode? I did update the graphics card and it was fine until I did an OS update. I was running Mavericks.

what graphics card is in the machine now?

Have you ever seen it work?

it worked fine until I ran a Mac OS software update. It's a GeForce gt630. I was able to target disk mode to get my files but no luck with safe boot or boot from disk?

I expect that is not a "Mac Edition" card. These card generally do not show:

Normal Startup until you get the Driver loaded-- at the login screen or Desktop

Alt/Option Boot

Installer

Recovery Mode

Safe Boot

NVIDIA cards after about 10.8.3 did tend to show normal screens. What Mac OS X did you upgrade to?

It's ridiculous all I did was run the recommended update on Mavericks and then boom my video card doesn't respond when I used it for the last six months. What I take from it is if you ever buy an Apple computer don't expect to do upgrades on it because it's not reliable. The only time I can even respond on this post is on my computer because Safari on my iPhone will keep crashing every time. now the only solution I could possibly figure out even speaking to an Apple technician is finding an original graphics card which is ancient who's gonna have and then I have to plug it in restored to factory settings then do the upgrade again reinstall my graphics card it's really really frustrating and sad

Be sure you have done an SMC Reset along the way.

Command option P and R I did it about three times you'll hear the reboot chime go again and still nothing it's really stupidly frustrating

This is the standard procedure for SMC reset:

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

Desktop Mac owners find they get better results by adding this step:

2a. With AC power removed, press the power-on button for five seconds (or more) to completely discharge the power capacitors.

Which OS version (Yosemite? Lion? etc) and the gpu should be front-and-center if different from the original post (which lacked details also).

Some of the mystery behind and experience of others:

http://forums.macrumors.com/showpost.php?p=20703758&postcount=1939

http://forums.macrumors.com/showthread.php?t=1440150&page=78

Some got tired of all the issues with "unsupported" and have gotten either EVGA Mac or flashed a PC GTX 680 to avoid problems.

My own "rule number one" is to always have a bootable clone backup of current system, and only then apply updates.

In the past it was possible to apply updates to non-boot drive, even a sparse disk image, and leave the working boot system untouched, that nice feature got taken away, making a clone even more important. There are no painless updates and actually security updates have a habit and long history of breaking more things than a "regular" system update. Not sure why but see that reported all the time. Which is why some like to even hold off for a week, though of course we all are told how security updates should not be deferred, though prudence in applying and being sure it doesn't break essential programs and hardware is as if not more important.

So I always read up on a couple good Mac feedback news sites.

I added the old graphics card that I borrowed and I can now see the screen but I keep getting the? In the folder I tried booting in recovery have tried booting in safe mode I tried booting from auction and I still can't get past that I even have a CD of snow leopard in the city tree and it won't recognize when I boot from holding c?

every time you reset nvram you need to reset the Startup Disk, even take the drive volume off the high-lighted selection, then choose it again.

begins to sound like the disk drive itself.

Yes, the problem with a non-EFI card is that the second you have an OS issue, the computer becomes completely unusable or unfixable.

Running a GT630 is fine, but you should keep a cheapie EFI card around for future issues. An AMD 2600XT for Mac is a good choice as it works in ALL Mac Pro towers. A GT120 is also a good choice, but if it is a flashed one, need to be sure it is for your gen of Mac. (EFI32 vs EFI64)