Gigabyte 990FXA-UD5 Motherboard
By Gabriel Torres on June 15, 2011


So far, Gigabyte has released four motherboards based on the new AMD 990FX chipset, and today we are taking a look at one of the models targeted to the entry high-end market, the 990FXA-UD5, which comes with five PCI Express x16 slots.

The AMD 990FX chipset is basically an AMD 890FX chipset with a new name. There are no new features. The AMD 990FX chipset, however, is targeted to the new socket AM3+ platform, while the 890FX chipset is targeted to the socket AM3 platform. This way, AMD is providing an easy way to identify the platform through the chipset name. Socket AM3+ motherboards support the forthcoming AMD CPUs based on the new “Bulldozer” architecture. So, even though the chipset is the same, 890FX motherboards won’t support this new generation of AMD processors.

Gigabyte 990FXA-UD5 motherboard
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Figure 1: Gigabyte 990FXA-UD5 motherboard


The Gigabyte 990FXA-UD5 comes with five PCI Express x16 slots, one PCI Express x1 slot, and one standard PCI slot.

The first PCI Express x16 slot (PCIEX16_1) always runs at x16 speed; the second PCI Express x16 slot (PCIEX4_1) always runs at x4 speed; the third PCI Express x16 slot (PCIEX16_2) always runs at x16 speed; the fourth PCI Express x16 slot (PCIEX4_2) always runs at x4 speed; and the fifth PCI Express x16 slot (PCIEX8) always run at x8 speed. This way, in order to achieve the best performance if you are installing two video cards, you should install them in the first and third slots, not in the first and second slots as it would appear more logical.

There is no space between the PCI Express slots, so if you install a dual-slot video card in any PCI Express x16 slot, you will “kill” the slot right next to it.

All PCI Express x16 slots support both CrossFireX and SLI modes.

Gigabyte 990FXA-UD5 motherboard
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Figure 2: Slots

Memory Support

AMD CPUs have an embedded memory controller, meaning that it is the processor – and not the chipset – that defines what memory technologies and the maximum amount of memory you can have. The motherboard, however, may have a limitation as to how much memory can be installed.

Currently, the integrated memory controller of AMD processors support only DDR3 memories up to 1,333 MHz under dual-channel architecture, but Gigabyte says the 990FXA-UD5 supports memory up to 2,000 MHz through overclocking.

The Gigabyte 990FXA-UD5 has four memory sockets and, since DDR3 memory modules can now be found in capacities up to 8 GB, you can have up to 32 GB with this motherboard if you use four 8 GB modules.

Gigabyte made the bad decision of having painting all of the memory sockets black. You have to skip one socket when installing only two memory modules, otherwise your memory will use single-channel mode. If the first and third sockets were painted in one color, and the second and fourth in another, it would be easier to identify which sockets to use.

Gigabyte 990FXA-UD5 motherboard
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Figure 3: Memory sockets; install two or four modules for the best performance

On-Board Peripherals

The AMD 990FX chipset is a two-chip solution. The south bridge chip is an SB950 chip, which is a renamed SB850. This chip supports six SATA-600 ports, supporting RAID (0, 1, 5 and 10).  The 990FXA-UD5 has two additional SATA-600 ports, controlled by a Marvell 88SE9172 chip, supporting RAID 0 and 1. These ports are located on the motherboard edge rotated 90°, so video cards won’t block them.

Gigabyte 990FXA-UD5 motherboard
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Figure 4: SATA-600 ports

The portrayed motherboard also has two eSATA-600 ports, controlled by another Marvell 88SE9172 chip, supporting RAID 0 and 1. There is no support for a floppy disk drive controller or an ATA-133 port.

This motherboard has 14 USB 2.0 ports, eight soldered on the rear panel and six available through three headers located on the motherboard. It also has four USB 3.0 ports, controlled by two EtronTech EJ168A chips. Two ports are located on the motherboard rear panel, and two are located on a front panel header.

The 990FXA-UD5 has two FireWire (IEEE1394) ports, one at the motherboard rear panel and one available at a header on the motherboard. These ports are controlled by a VIA VT6308P chip.

This motherboard supports 7.1+2 audio format, i.e., eight channels plus two independent channels for audio streaming. On this motherboard, the audio is generated by the chipset using a Realtek ALC889 codec, which is an outstanding solution, providing an impressive 108 dB signal-to-noise ratio for the analog outputs, 106 dB signal-to-noise ratio for the analog inputs, and up to 192 kHz sampling rate for both inputs and outputs. This means you are able to capture and edit analog audio (e.g., converting LPs to CDs or MP3, converting VHS to DVDs or any other digital format, etc.) with this motherboard without adding any background noise.

The portrayed motherboard comes with independent analog audio outputs and an optical SPDIF output. You can add a coaxial SPDIF output or route digital audio to your video card to have digital audio in the HDMI connector using the available “SPDIF_O” header.

This motherboard has one Gigabit Ethernet port, controlled by a Realtek RTL8111E chip.

In Figure 5, you can see the motherboard rear panel, with PS/2 keyboard and mouse shared connector, eight USB 2.0 ports, optical SPDIF connector, FireWire port, two eSATA-600 ports, one Gigabit Ethernet port, two USB 3.0 ports (blue), and independent analog 7.1 audio outputs.

Gigabyte 990FXA-UD5 motherboard
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Figure 5: Motherboard rear panel

Other Features

The Gigabyte 990FXA-UD5 has other features. The most important is the presence of two BIOS chips. If the main BIOS is corrupted by an unsuccessful BIOS upgrade or virus, you can still turn on your PC and fix the defective BIOS using the backup chip.

Gigabyte 990FXA-UD5 motherboard
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Figure 6: Two BIOS chips

The motherboard has a legacy serial port on a header labeled “COMA.” You will need to buy an adapter if you want to use this port.

In Figure 7, you can see all the accessories that come with this motherboard.

Gigabyte 990FXA-UD5 motherboard
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Figure 7: Accessories

Voltage Regulator

The CPU voltage regulator circuit of the 990FXA-UD5 has eight phases for the CPU main voltage (VDD a.k.a. Vcore) and two for the CPU VDDNB voltage (integrated memory controller, HyperTransport bus controller, and L3 memory cache). Therefore, it uses an “8+2” configuration.

Gigabyte 990FXA-UD5 motherboard
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Figure 8: Voltage regulator circuit

Gigabyte 990FXA-UD5 motherboard
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Figure 9: Voltage regulator circuit

This motherboard uses solid ferrite-core coils, which present less energy loss than iron-core coils (i.e., they improve efficiency), and solid capacitors. Each main phase is controlled by an SiC769CD integrated circuit, which combines the three required transistors (“high side,” “low side,” and “driver”) in a single chip. It also allows the switching clock to be at 1 MHz, which allows efficiency to be over 90%. (Usually, voltage regulator circuits switch at 250 kHz.) Integrated circuits with those characteristics are known as “DrMOS.”

If you want to learn more about the voltage regulator circuit, please read our tutorial on the subject.

Overclocking Options

The Gigabyte 990FXA-UD5 offers some overclocking options, listed below (F3 BIOS):

For a better understanding of what these options do, please read our Understanding All Voltage Configurations from the Motherboard tutorial.

Gigabyte 990FXA-UD5 motherboard
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Figure 10: Overclocking options

Gigabyte 990FXA-UD5 motherboard
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Figure 11: Overclocking options

Main Specifications

The main specifications for the Gigabyte 990FXA-UD5 motherboard include:

* Researched at Google Shopping on the day we published this First Look article.


We were quite impressed by the Gigabyte 990FXA-UD5, with its five PCI Express x16 slots, two FireWire ports, four USB 3.0 ports, eight SATA-600 ports, two BIOS chips, professional-grade audio quality with optical SPDIF output, and a very high-end voltage regulator circuit.

Of course, it is not the cheapest motherboard around, but it comes with a fair price for its set ofall of its features.

Compared to its main competitor, the MSI 990FXA-GD80, the Gigabyte 990FXA-UD5 is a no-brainer, as it brings many more features at a similar price. Plus In addition, it uses a better audio codec. It is true, hhowever, that the MSI model has more overclocking options.

The only drawback we see with the 990FXA-UD5 is the fact that all of the memory sockets are black, and users may inadvertently install memory modules sequentially, making causing the memory to run at single-channel mode instead of dual-channel.

Even though the Gigabyte 990FXA-UD5 is mainly targeted to the forthcoming CPUs based on the AMD “Bulldozer” architecture, it is already available on the market, supporting current-generation CPUs.

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