The Asus M4A79 Deluxe is the first Socket AM2+ motherboard we've seen that is intended to accommodate both existing Socket AM2+ and upcoming Socket AM3 Phenom processors.
You see, Socket AM2+ Athlon X2 and Phenom processors have 940 pins and their integrated memory controllers can support up to DDR2-1066MHz RAM. Meanwhile, the the new Socket AM3 CPUs use 938 pins and are pin-compatible (i.e. they fit) with AM2+ sockets. They also have memory controllers that support both DDR2-1066MHz and DDR3-1333MHz system memory. The result is you should, in theory, be able to use the new AM3 CPUs in existing AM2+ motherboards, just with the limitation that you'll only be able to use the DDR2 memory that these older motherboards support. Oh, and you'll almost certianly need to update your motherboard's BIOS.
Of course, there will be many motherboards that this won't work for so you'll have to check out the motherboard manufacturer's website to see if you're board is one of the lucky ones. Either that or you could invest in one of Asus' new range of M4 motherboards that have been specifically developed to support just the above scenario.
The M4A79 Deluxe, then, is based on the existing AMD 790FX chipset and supports DDR2 memory. It's one of eight new models that come under the M4 moniker; the other seven being made up of four further models using AMD chipsets and three using nVidia chipset.
What we have here is a motherboard that looks very similar to the M3A79-T Deluxe with the addition of a more sophisiticated eight+two-phase power arrangement. Naturally the chipset cooler has undergone some cosmetic changes but we're used to that with Asus; they must have a squad of people churning out heatpipes, coolers and cosmetic tinware just to ensure us plebs can see a difference between its myriad motherboards.
If you do look closely you can spot a number of tiny changes between the two models. For instance the M3A79-T has a single PS/2 port that is two-tone green and purple to show that it can be used for either mouse or keyboard while the new M4A79 Deluxe has two PS/2 ports. Even ignoring the fact it has been ages since we last saw a PS/2 mouse, it's odd that the newer version would be more accomodating of older technology - most puzzling!
In another strange move the floppy drive connector (another anachronism, surely?) and Firewire header have swapped positions. This doesn't seem to make the blindest bit of difference to the ease of assembly and there seems little other reason why one would move them.
One change that really puzzles us is the SATA arrangement. The M3A79-T Deluxe has six SATA ports on the SB750 Southbridge with an eSATA port on a Marvell controller. By contrast the M4A79 Deluxe has five SATA ports and one eSATA running off the SB750 which means it has managed to do away with the Marvell chip. We feel that five internal SATA ports offer plenty of storage options so the change from seven ports to six is fine by us. Where we have a problem is with the configuration of the SATA ports. M3A79-T Deluxe has the six ports laid down in three blocks of two but the new board only has two laid-down ports while the other three stand vertical.