Does Crossfire need a bridge like SLI?

yes, you need a crossfire bridge

a 4870 has dual-monitor support with just one card

Does the hd4870 come with the bridge? I did not think that the 4870 had eyefinity. If he is running mulri-monitor with two cards will he still get the Crossfire power?

Most ATI cards come with bridges as far as I'm aware. They always came with ATI cards I've purchased.

2 monitor support for your desktop is not the same as eyefinity, which does need one of the 5xxx or 6xxx cards.

Also, Crossfire does not function in windowed mode. When he's using his monitors for his extended desktop, it will not be using crossfire.

Crossfire will work when he's in fullscreen mode playing a game. However, that fullscreen will only be 1 monitor, which ever is his primary display.

K thanks. If he got both the hd4870s would he be able to do 4 monitors?

Crossfire bridge is being included with the card less and less. Last two cards I bought did not come with it (Thanx a lot XFX). Just make sure they are included. They may come packaged with the mobo as well.

I believe it may be possible, but he could not use 4 monitors and Crossfire at the same time. While in Crossfire mode, only 1 card's ports are usable. If 4 monitors can work, crossfire would have to be disabled, so you can use them independantly.

Alright thanks for the help! =D

Imho, it was XFX and newegg that started omitting the bridges with ATI cards. Probably to shave a few dollars off.
They historically came with every ATI card, and you got your SLI bridge with your m/b purchase.