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[nextpage title=”Introduction”]
Intel has released two motherboard models for the new socket LGA2011 platform, the DX79SI and the DX79TO, targeted to the most high-end processor Intel offers for desktops today, the Core i7 “Sandy Bridge-E” models. Let’s take a look at the DX79SI, which comes with three PCI Express 3.0 x16 slots.
To better understand the differences between the two socket LGA2011 motherboards released by Intel, we compiled the table below.
| DX79SI | DX79TO | |
| Form Factor | ATX | ATX |
| Memory Sockets | 8 | 8 |
| PCI Express x16 | 3 (x16/x16/x8) | 2 (x16/x16) |
| PCI Express x1 | 2 | 3 |
| Standard PCI | 1 | 1 |
| SATA-300 | 4 | 4 |
| SATA-600 | 2 | 2 |
| eSATA-600 | 0 | 0 |
| USB 2.0 | 14 | 14 |
| USB 3.0 | 4 | 2 |
| FireWire | 2 | 0 |
| Gigabit Ethernet | 2 | 1 |
| Wi-Fi IEEE 802.11b/g/n | Yes | No |
| Bluetooth 2.1 | Yes | No |
| Price | USD 280 | USD 230-250 |
In Figure 1, you see the Intel DX79SI motherboard.
Figure 1: Intel DX79SI motherboard
[nextpage title=”Slots”]
The Intel DX79SI comes with three PCI Express 3.0 x16 slots, two PCI Express 2.0 x1 slots, and one standard PCI slot. Socket LGA2011 processors have a total of 40 PCI Express 3.0 lanes for video cards. This allows a very high-end configuration for the PCI Express x16 slots, but the exact configuration used will depend on the motherboard model.
The first and second PCI Express x16 slots always run at x16 speed, while the third PCI Express slot always works at x8 speed.
When installing dual-slot video cards, you “kill” the slot immediately to the left (looking at the motherboard with its rear connectors facing up) of the slot being used. The installation of three dual-slot video cards can be done using a regular seven-slot case.
All PCI Express x16 slots support both SLI and CrossFireX technologies.
Figure 2: Slots
[nextpage title=”Memory Support”]
Intel socket LGA2011 CPUs have an embedded memory controller, meaning that it is the processor, not the chipset, which defines what memory technologies you can have and the maximum amount of memory that is possible. The motherboard, however, may have a limitation as to how much memory can be installed.
The integrated memory controller from socket LGA2011 processors supports DDR3 memories up to 1,600 MHz officially, but they actually support memories up to 2,133 MHz. According to Intel, the DX79SI supports memories up to 2,400 MHz.
One of the most important features of the socket LGA2011 processors is the support for the new quad-channel memory architecture, which allows the memory to be accessed in 256-bit mode for higher performance. Since each memory module is a 64-bit entity, four memory modules are needed to enable this architecture. If only two or three memory modules are installed, the memory will be accessed under dual- or triple-channel architecture, respectively. If you want to have more than four memory modules installed, you will have to install eight memory modules.
The Intel DX79SI has eight memory sockets (four at each side of the CPU socket) and, since DDR3 memory modules can be found in capacities up to 8 GB, you can have up to 64 GB with this motherboard if you use eight 8 GB modules.
In order to enable the quad-channel mode, install four identical memory modules in the sockets with the same color. If you want to install more modules, install another group of four memory modules in the sockets that use the other color.
Figure 3: Memory sockets; install four or eight modules for the best performance
[nextpage title=”On-Board Peripherals”]
The Intel X79 chipset is a single-chip solution which is also known as a PCH (Platform Controller Hub). This chip supports two SATA-600 ports and four SATA-300 ports, supporting RAID (0, 1, 10, and 5). The SATA ports are located at the motherboard’s edge and rotated 90°, so video cards won’t block them. See Figure 4.
Figure 4: SATA-300 (black) and SATA-600 (blue) ports
The Intel DX79SI doesn’t carry extra SATA or eSATA ports.
The Intel X79 chipset supports 14 USB 2.0 ports. Unfortunately, support for USB 3.0 ports isn’t integrated in the chipset yet. The Intel DX79SI offers all 14 USB 2.0 ports, six soldered on the rear panel and eight available through four headers located on the motherboard. It also supports four USB 3.0 ports, controlled by two NEC (Renesas) µPD720200 chips. Two of them are located on the motherboard rear panel and the other two are available on a motherboard header, to be used by USB 3.0 ports located on your computer case.
The Intel DX79SI has two FireWire ports, one soldered on the rear panel and one available on a motherboard header. They are controlled by a VIA VT6315N 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 the Realtek ALC892 codec. The specifications of this chip include a 97 dB signal-to-noise ratio for the analog outputs, a 90 dB signal-to-noise ratio for the analog inputs, up to 192 kHz sampling rate for both inputs and outputs, and 24-bit resolution. We don’t understand why Intel decided to use a mainstream audio codec on a high-end motherboard. They should have picked a codec with an SNR of at least 100 dB for the analog outputs and 97 dB for the analog inputs. If you are looking into working professionally with audio editing, you should look for a motherboard that provides an SNR of at least 97 dB for the analog input.
This motherboard comes with independent 5.1 analog audio outputs. However, if you install a 7.1 analog speaker set, you will have to use either the line in or mic in jacks, making the jack unavailable for other usage. It also features optical SPDIF output, and you can install a coaxial SPDIF output through an SPDIF header that is available, using an adapter that doesn’t come with the product.
The portrayed motherboard has two Gigabit Ethernet po
rts, one controlled by the chipset using an Intel WG82579LM chip to make the interface with the physical layer and the other controlled by an Intel WG82574L controller. This motherboard also comes with a Bluetooth 2.1 and Wi-Fi IEEE 802.11b/g/n module. This module is connected to one of the motherboard USB 2.0 headers.
In Figure 5, you can see the motherboard rear panel, with the “Back-to-BIOS” switch, two USB 3.0 ports, six USB 2.0 ports, two Gigabit Ethernet ports, one FireWire port, shared 7.1 analog audio jacks, and an optical SPDIF output.
Figure 5: Motherboard rear panel
[nextpage title=”Other Features”]
As you may have seen in Figure 5, the Intel DX79SI has a switch called “Back-to-BIOS,” which allows you to enter the motherboard setup immediately upon turning on or restarting your computer.
This motherboard has a POST diagnostics display, which shows, through a two-digit code, which component is preventing the computer from turning on.
Figure 6: POST diagnostics display
It also has a series of diagnostics LEDs that give you some extra debugging information, such as if the CPU or voltage regulator circuit is facing an overheating problem.
Figure 7: Diagnostics LEDs
The motherboard also has an infrared interface, making it inexpensive for you to add an infrared sensor to be able to use a remote control or to connect devices using infrared technology (IrDA).
The product also comes with a thermal sensor, so you can monitor the temperature of any component you want.
[nextpage title=”Voltage Regulator”]
The CPU voltage regulator circuit of the Intel DX79SI has six phases for the CPU main voltage (Vcc a.k.a. Vcore), one for the CPU VSA voltage (memory controller), and one for the CPU VTT voltage (PCI Express and DMI interfaces). Therefore, it uses a “6+1+1” configuration. The voltage regulator is controlled by a CHiL CHL8328 integrated circuit.
Figure 8: Voltage regulator circuit
All electrolytic capacitors used in the main voltage regulator circuit are SMDs (surface mount devices), also known as highly-conductive polymerized or simply Hi-c, but the other voltage regulators (memory, chipset, etc.) use solid capacitors. All coils on this motherboard are ferrite-core models, which can provide up to 20% improvement in efficiency.
Each main phase is controlled by a Renesas R2J20657 integrated circuit (click here for a detailed description), 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 percent. (Usually, voltage regulator circuits switch at 250 kHz.)
If you want to learn more about the voltage regulator circuit, please read our tutorial on the subject.
[nextpage title=”Overclocking Options”]
The Intel DX79SI has a few overclocking options. Below, we list the most important ones (S1.0280B BIOS):
- CPU base clock: From 89.93 MHz to 146.98 MHz in 0.23 MHz increments
- CPU core voltage: From 1.000 V to 1.920 V in 0.005 V increments
- Memory controller (“System Agent”) voltage: From 0.8500 V to 1.8000 V in 0.0125 V increments
- CPU VTT (“I/O”) voltage: From 1.0500 V to 1.8000 V in 0.0125 V increments
- CPU PLL voltage: From 1.8000 V to 2.0000 V in 0.0125 V increments
- Chipset (PCH) voltage: From 1.1000 V to 1.5000 V in 0.0125 V increments
- Memory voltage: From 1.2000 V to 1.9250 V in 0.0125 V increments
Figure 9: Overclocking options
Figure 10: Overclocking options
Figure 11: Memory timing adjustments
[nextpage title=”Main Specifications”]
The main specifications for the Intel DX79SI include:
- Socket: 2011
- Chipset: Intel X79 Express
- Super I/O: Winbond W83677HG
- Parallel ATA: None
- Serial ATA: Four SATA-300 ports and two SATA-600 ports controlled by the chipset (RAID 0, 1, 10, and 5)
- External SATA: None
- USB 2.0: 14 USB 2.0 ports, six soldered on the motherboard rear panel and eight available through four headers on the motherboard
- USB 3.0: Four USB 3.0 ports controlled by two NEC (Renesas) µPD720200 chips, two on the rear panel and two on a motherboard header
- FireWire (IEEE 1394): Two ports, controlled by a VIA VT6315N chip, one on the motherboard rear panel and one available on a motherboard header
- On-board video: No
- On-board audio: Produced by the chipset together with a Realtek ALC892 codec (7.1+2) channels, 24-bit resolution, up to 192 KHz sampling rate for both the inputs and outputs, 90 dB signal-to-noise ratio for the inputs and 97 dB signal-to-noise ratio for the outputs), on-board optical SPDIF output
- On-board LAN: Two Gigabit Ethernet ports, one controlled by the chipset with an Intel WG82579LM physical layer interface chip and one controlled by an Intel WG82574L controller, and a Wi-Fi IEEE 802.11b/g/n module
- Buzzer: Yes
- Infrared interface: Yes
- Power supply required: EPS12V
- Slots: Three PCI Express 3.0 x16 slots (x16/x16/x8, supporting SLI and CrossFireX),
two PCI Express 2.0 x1 slots, and one standard PCI slot - Memory: Eight DDR3-DIMM sockets (up to DDR3-2400, 64 GB maximum)
- Fan connectors: One four-pin connector for the CPU cooler and three four-pin connectors for auxiliary fans
- Extra features: POST diagnostics display, diagnostics LEDs, Back-to-Bios switch, Bluetooth 2.1
- Number of CDs/DVDs provided: One
- Programs included: Motherboard utilities
- More Information: https://www.intel.com
- Average price in the US*: USD 280.00
* Researched at Newegg.com on the day we published this review.
[nextpage title=”Conclusions”]
Intel-branded motherboards are usually plain and generally targeted to conservative users. These users want to have the peace of mind knowing that the motherboard in their computers was designed by the same company that manufactured the processor.
Intel usually takes a conservative approach when designing their motherboards, but the Intel DX79SI has some advantages over its competitors, such as the included Wi-Fi IEEE 802.11b/g/n and Bluetooth 2.1 module, the presence of two Gigabit Ethernet ports, the two FireWire ports, eight memory sockets, and the support for three-way SLI and CrossFireX without the need for a case with more than seven expansion slots.
The drawbacks of this motherboard include the absence of extra SATA ports and eSATA ports, the use of a mainstream audio codec instead of a high-end one, and fewer overclocking options compared to the competition. The voltage regulator circuit available on the Intel DX79SI is very good, but competing products offer even better designs.
In summary, the Intel DX79SI is a fair-priced, good option for the new LGA2011 platform. Only you will be able to choose if you prefer the Wi-Fi/Bluetooth module instead of more SATA ports.