The M4A89GTD Pro/USB3's PCIe and PCI slot setup is very unusual. From top to bottom we have a PCIe x16 slot (white), followed by PCIe x1, PCIe x4, a second PCIe x16 slot (blue) and two standard PCI slots. When I initially saw this design I was surprised that Asus would have chosen to obscure a PCIe slot rather than a PCI one when installing a dual-slot video card, but as it turns out, this is not the case. Following the colour-coding of the rest of the board, the primary graphics card slot is actually the second (blue) one, and to make things even odder you need to leave the provided daughter card installed on the first slot to give a single card its full x16 bandwidth.
While unintuitive, this setup doesn't really detract from the M4A89GTD Pro/USB3 in any functional way. As the two full-length graphics card slots suggest, the board is CrossFireX compatible, and though in CrossFire mode the two graphics card slots will only provide x8 each, that should be adequate for all but the highest-end video cards.
Moving on to the rear I/O, we have pretty much every connection you could need or want. Thankfully, manufacturers have finally cottoned on to the fact that two PS2 ports is overkill in this day and age, and aside from a single PS2 port (which can be genuinely useful) there are no legacy ports wasting valuable space here. For video we have VGA, DVI and HDMI 1.3 while audio outputs are on hand in both digital optical and six-jack analogue for eight-channel surround sound, courtesy of a Realtek ALC892 HD Audio Codec. These are joined by a Gigabit Ethernet port, four USB 2.0 and two USB 3.0 connections (with the latter marked in their universal blue livery) and last but not least a green eSATA port.
On the software side of things, Asus' BIOS is as comprehensive as we've come to expect from the company, although layout isn't as clear as on some of its boards. As usual, the A.I Tweaker menu is the main port of call for enthusiasts, where a veritable trove of overclocking options awaits, all assignable to eight different profiles.
Before we check out the M4A89GTD Pro/USB3's overclocking performance, it's worth noting what for many will be its most interesting feature: the aforementioned core unlocking. As AMD has killed off Advanced Clock Calibration support on its new chipsets, it's up to individual motherboard manufacturers to find ways of implementing the core unlocking feature, and we can confirm that Asus' way works.
Putting in a Phenom II X3 720 and flicking the core unlocking switch resulted in the board recognising this as an X4 chip, with the splash screen displaying the message that the unlock had been successful. Unfortunately the fourth core on our test CPU had apparently been binned with good reason, as it failed to let the test machine boot into Windows. Still, if you're lucky you essentially get quad-core performance for a tri-core price.
Conversely, as well as using core unlocking to activate a fourth core, you can de-activate any active cores of your choice. The use of this may be limited, but as AMD processors can't completely shut down a CPU core like Intel's Core i family does, you could create a dual-core profile on your quad-core CPU for better energy saving.