virtualbox.org

Which network adapter built-in VirtualBox supports Bootrom?AMD or Intel

Are you referring to a network (PXE) boot? I wouldn't have thought the adapter type mattered. The user manual doesn't mention a preference, it just says that it's network cards (note plural) supports it. In another section it mentions the Intel (E1000) card specifically, so I guess I would go with that.

You also need to install the extension pack.

Sorry I mean BootRom ,boot from SAN.
When I create a VM with a intel network adapter and no disk .
I configure VM boot from network,it always reports “Fatal, No bootable medium found! System halted”
But once I change to AMD network adapter, it shows normally

What is "SAN"?

Sorry, as I mentioned I don't use the PXE boot feature, and doubt I ever will. If anyone else uses it, and if that is indeed what you're talking about then perhaps they can help you. Though if you're saying that it works with AMD then I'm not sure why you aren't happy with that.

Thanks mpack.
Actually I had another problem viewtopic.php?f=2&t=57321 posted on windows guest.
Since AMD network adapter supports booting from SAN ,so I have to upload the win7 VM with AMD adapter supported and this is why win7 VM has to use the specified card.
This really confuses me ...
Thankes mpack, any help will be appreciated...

VirtualBox does not support "boot from SAN". It does support PXE booting. And as others mentioned, PXE boot using the emulated Intel NICs requires the Extension Pack to be installed.

But please get your terminology straight. It's very hard to help you without having any clue what you're actually talking about.