@MrPippy: Thank you!  Your link shows how to modify the source code of

my kernel, but rather than go that route, it gave me enough info to find

the ATI site where they have posted RPMs for various cards.

I did the following on my CentOS 7 box:

- I downloaded https://www2.ati.com/drivers/linux/fglrx64_p_i_c-15.302-1.x86_64_rhel7_64a.rpm

- I installed all the missing dependencies (note: you also need redhat-lsb-core)

- Then:

  % rpm -Uvh fglrx64_p_i_c-15.302-1.x86_64_rhel7_64a.rpm

  Preparing...                          ################################# [100%]

  Updating / installing...

     1:fglrx64_p_i_c-15.302-1           ################################# [100%]

  /usr/libexec/plymouth/plymouth-populate-initrd: line 233: dfatal: command not found

  /usr/libexec/plymouth/plymouth-populate-initrd: line 234: dfatal: command not found

  /usr/libexec/plymouth/plymouth-populate-initrd: line 235: dfatal: command not found

  /usr/libexec/plymouth/plymouth-populate-initrd: line 236: dfatal: command not found

  /var/tmp/rpm-tmp.ahgIOH: line 1171: lsb_release: command not found

  ....

  <reboot>

  % aticonfig --initial

  % startx

Then I added a wireless keyboard and mouse plugged into a USB card

that's also passed through to the VM.  Success!  I can run `startx` from

the console and X11 runs on the Radeon display.

Now I've advanced to the next problem.  When I change the system default

to graphical:

  % systemctl set-default graphical.target

and reboot, I get a screen that says, "Oh no! Something has gone wrong."

So the problems continue ....