NetBooting older Macs


I recently came into possession of a Mac Pro and have loaded a copy of Mac OS X Server 10.6.6 onto it. The primary purpose of this system is to be an AST and imaging server, but also probably a workstation.

I've gone and set up the NetBoot server, and created a bunch of netinstall images of various restore media, including a copy of the retail 10.6 disc. Right now everything is just a direct connection via ethernet cable.

This afternoon, I had to replace the HDD on a Mid-2007 iMac, so figured I'd use the new server to install the OS using the retail 10.6 image. So I plug in the ethernet cable, hold down the option key to get the EFI boot selector, and... Nothing. I waited a good 5-10 minutes, still nothing showed up.

I boot off an external HDD, go to the startup disk preference pane, it sees the netinstall image almost immediately, but when I try rebooting using it, nothing. It ultimately times out and gives me the flashing question mark folder.

Looking at the logs of the server, it appears as if it's trying to send the boot rom file to the system, but for whatever reason it's not accepting it.

So, in my attempt to figure out if maybe my ethernet cable went bad, I grabbed a Mid-2010 MBP, and start it up. It finds the netinstall image almost immediately.

Also, a slightly odd behavior I've never seen before. At one point when I held down the option key, I could see a netboot image icon at the boot selector. However it was flashing, and I could not select it. After a time it went away.

All of this leaves me wondering why new systems have no problems picking up on these images, but older systems do not. Apple's documentation is essentially worthless, and I can't seem to really find anything with Google. Anyone have any thoughts, or better yet, solutions they'd care to share?

And as a couple of side questions, is there some upper limit to the number of boot options the EFI boot selector will show? I work at an AASP, and have systems that run the gamut of all the Intel models original to the Late 2010 MacBook Airs. Ideally I'd like to have restore media available for all of them, or at least the ones that are too new for a retail disc. I'd also like to have netbootable images of ASD OS (which despite Apple's claims, CAN be netbooted) until they get around to folding them into AST. Also, is there a way to set a priority on images, so I can pick the first 8 images that show up before it takes a couple minutes to find the rest? Something that doesn't involve me having to disable and enable images as I need them?