Gigabyte have been using digital VRMs for quite a while now, so it will be interesting to see what should be one of the more mature implementations of it. The Z77X-UD5H boasts a “12 phase CPU VRM” but they actually could have called it 15 phase, depending on how you count them. Other companies certainly count all three rails together. The overall CPU VRM comes in a 12+2+1 configuration to VID + VAXG + VCCIO. Let’s map everything out:
The main PWM is an International Rectifier IR3567A 6+2 Phase Digital PWM – 6 channels go to VID, which is the ‘main CPU voltage’ shown in red, and the other two go to VAXG, which is the integrated GPU, shown in blue.
You might wonder how they get 12 phases from a 6 phase PWM. The truth is that each phase goes through an IR3598 MOSFET driver/doubler. This doubles each phase, spreading the load of each across 6 MOSFETS instead of 3. By spreading the load so widely, heat and power capacity of the VRM are kept in check. Keep in mind though, that this does now lower ripple frequency. With 6 ‘true’ phases however, that is not a concern for all but extreme overclockers (think liquid nitrogen). This isn’t like some other manufacturers who use doublers with 4 phases to claim they have an 8 phase VRM on the box rather than using an 8 phase PWM.
The VAXG rail gets the remaining two phases from the PWM. This is sent to a single IR3598, but this one is in double-driver mode, rather than doubler mode. It is taking both phases, and driving both sets of MOSFETs.
The VCCIO phase in yellow, and the DDR phase in green are both controlled by an IR3570 PWM 3+2 phase PWM that sits right below the DIMMs in the picture above (apologies for cutting it out of the picture). This means that the Z77X-UD5H is one of the few now that has a truly fully digital VRM for all its main components. This is pretty rare (another board that does this is the EVGA Z75 SLI) but will eventually become the norm. Only one phase is used for VCCIO, driven by a CHL8550, and the DDR phases are driven by another IR3598 in double driver (not doubler) mode.
Here’s a closer look at two of the CPU phases. On the very left is the IR3598 doubler/driver. This splits the phase into two, where you have two Renesas K0393 low side PowerPAK MOSFETS (one is on the other side of the board) and one Renesas K03B7 high side MOSFET. Each group of MOSFETS is good for around 25 amps, depending on temperature. Multiply that by 12 phases, and you have a board that is capable of pushing 300 amps to the CPU while remaining cool and stable.
Z77X-UD5H Component Tour
Now we’ll proceed with our motherboard tour, looking at every onboard component in full detail. Keep in mind that this is a revision 1.0 board – the 1.1 version you’d find in stores today have a few minor differences, which we’ll let you know about as we come across them.
The Z77X-UD5H has two Ethernet ports, one controlled by an Intel WG82579 and one controlled by a Qualcomm Atheros AR8151. The revision 1.1 board updates this to an Atheros AR8161. As far as I can tell, no major improvements have been made. In fact, there is no acknowledgement of its existence on the Atheros website.
These two VIA VL810 hubs are what allows the Z77X-UD5H to have more USB 3.0 ports than most in its class – 10 in total. Each one takes a single Intel USB 3.0 port, and splits it into four full speed downstream ports. Revision 1.1 of the board uses VL811 instead, which adds high current charging while maintaining full transfer speeds.
Audio is handled by a Realtek ALC898 codec, and a pair of TI DRV632 line drivers used as headphone amps (one for the front panel output, and one for the green port on the rear panel). The specs of the ALC898 are good as far as onboard audio goes; we’ll be testing it against other common solutions later on.
As is common for Gigabyte motherboards, the Z77X-UD5H’s Super IO duties are handled by a pair of ITE chips: the IT8728F and IT8892E. The former controls everything from fan headers, to hardware monitoring, and adds the board’s legacy devices (the PS/2 keyboard and mouse controller). The second chip converts one of the PCI-E lanes, and converts it to three legacy PCI lanes only two of which are used – one is used for the board’s single PCI slot, while the other goes to this:
A VIA VT6308P IEEE 1394 controller. I’m not exactly sure what the use of this is; my guess is that Gigabyte simply have a ton of them in stock, and don’t see any harm in including them on their boards. So there you go, a PCI FireWire controller in 2013.
Complimenting the PCH’s four SATA-300 and two SATA-600 ports are these Marvell 88SE9172 SATA-600 controllers. One controller adds a pair of internal SATA ports, while the other adds one internal and one eSATA port. These should only really be used as a last resort, or for external or optical drives. Intel’s controllers are much faster (even at SATA-300) as you’ll see later, and have the reputation of being more reliable.
Speaking of SATA, the Z77X-UD5H has an integrated mSATA slot, which can be used with drives like the Intel 525 SSD. This is more of a novelty than something really useful, considering this board will be sitting in a full sized ATX case. It shares the SATA5 port, which is a SATA-300 connection, so you won’t get full capabilities of a high capacity drive like the 180GB or 240GB Intel 525. It is only really intended to be used with smaller SSDs in cache mode.
One feature that is really useful is the Dual BIOS that has become the norm for Gigabyte motherboards. The Z77X-UD5H has an onboard switch, allowing you to manually switch between the backup and main BIOS between boots. There are even LED indicators to let you know which BIOS is being used. Very handy!
This concludes our motherboard tour, and as you can see, the Z77X-UD5H has some very cool components that were worth talking about. Next we’ll see how Gigabyte makes use of many of these components, as we look at their BIOS software bundle.