iXBT Labs - Computer Hardware in Detail






Intel D955XBK — a Motherboard Based on Intel 955X

In mid April Intel presented its first dual core Pentium processor Extreme Edition 840, and the announcement of the desktop Pentium D series is expected in the nearest future. It goes without saying that the new products are properly supported. Another generation of Intel chipsets — 945x/955X — is designed for motherboards supporting the new processors of this company. It's not surprising that the D955XBK motherboard from Intel has become the first such model.

First of all let's note that thanks to the Intel-NVIDIA cooperation the new i945 and i955X chipsets learned to support SLI mode, the eloquent proof of this support is two PCIEx16 slots (the second slot operates in x4 mode). More functionality is granted by a gigabit network adapter, an additional Serial ATA controller, a FireWire controller, and integrated High Definition Audio, based on the good SigmaTel codec. On the whole, it's a top Intel product, which will definitely have a negative effect on its price, though the D955XBK functionality and especially bundle are rather modest compared to top models from other manufacturers.

In general, the PCB layout is standard, though Intel often uses a design, when a full-sized ATX board can be reduced to a mATX model by "cutting off" a piece of PCB (e.g. Intel D925XCV). In such cases the cut-off-piece (the left part on the photo) contains almost no functional elements except for a couple of PCI slots and probably several connectors. But in our case we can see a sterling design that takes advantage of the entire PCB area. The first thing you notice about this motherboard is the abundance of power connectors and an unusually bulky and high pin-fin heatsink on the northbridge, which actually does not block non-standard CPU coolers except for those with very large heatsinks. You will inevitably pay for a lot of connectors at the right edge (on the photo) of the motherboard with a cable jungle. Plugging cables will also prove problematic. Besides, a video card in the main PCIEx16 slot will block memory modules in their slots. Moreover, a video card in the secondary PCIEx16 slot will rest on the southbridge heatsink.

The 4-phase switching voltage regulator of the processor incorporates one 3300 uF capacitor, four 1200 uF capacitors, and nine 560 uF capacitors. The PCB also contains a memory voltage regulator (incorporating two 3300 uF and eleven 100 uF capacitors), and PCIEx16 and DIMM circuits are reinforced with L elements for better operating stability. +5 V Standby on the motherboard is indicated by a green LED. Intel D955XBK is available in two modifications, the second one (LA955XBKLKR) is intended for system integrators, so it has no FireWire and [additional] SATA controllers, it's equipped with a simpler audio codec, but instead it offers such functions as iAMT (Intel Active Management Technology, remote control) for the network interface and TPM (Trusted Platform Module, integrated controller to verify digital signatures and keys as well as for other cryptography and security tasks). Motherboard dimensions – 305x245 mm (full-sized ATX, ten-screw mount, all motherboard edges are firmly fixed).

System monitoring:

  • CPU voltage, +1.5 V, +3.3 V, +5 V and +12 V
  • RPM of 3 fans
  • CPU and board temperatures (by the corresponding embedded sensors)

Onboard ports, sockets, and connectors

  • Processor socket (Socket 775 for Intel Pentium 4, Pentium D, Pentium 4 Extreme Edition, Pentium Extreme Edition — all top processors from this company are supported)
  • 4 x DDR2 SDRAM DIMM (up to 8 GB DDR2-533/667 with/without ECC Supports dual channel mode, the total memory capacity in both channels must be the same — for example, 256/256 or 256+256/512)
  • 2 x PCIEx16 (the second slot operates in x4 mode, it's intended for an additional video accelerator to organize SLI)
  • PCIEx1 slot
  • 3 x PCI
  • Power connectors: standard ATX 2.2 (24 pins; you can plug a regular 20-pin connector, but in this case you had better not use modern powerful components, like top PCIE video cards, or you will have to use the additional connector), 8-pin EPS12V to power up a processor (you can use an adapter from the 4-pin ATX12V connector), 4-pin (peripheral) additional connector for a PSU with 20-pin connector (it's mandatory for SLI mode)
  • 1 x FDD
  • IDE connector (Parallel ATA) for two ATA100 devices (in the chipset)
  • 8 x SATA (Serial ATA) for 4 SATA300 devices and 4 SATA150 devices — four of them are based on the chipset and support transfer rates of up to 300 MB/sec as well as other SATA-II functions; connected disks can form RAID 0, 1, 0+1 (10), and 5; the other four are based on an additional controller Silicon Image, supporting 150 MB/s transfer rates; connected disks can form RAID 0, 1, and 0+1
  • 2 connectors for brackets with 4 additional USB ports
  • 2 connectors for brackets with 2 Gigawire ports
  • Connector for a chassis intrusion sensor
  • On-board power connector (peripheral ATX) for internal illumination devices, additional fans, etc; low-level (maximum 1.5 A — you cannot plug hard drives, etc); it can be enabled or disabled on the software level (including via BIOS Setup)
  • 4 x fan connectors (three of them are with RPM control)

Back panel (left to right, blockwise)

  • PS/2 mouse and keyboard
  • 1 x LPT, 1 x COM, 1 x S/PDIF-Out (Coaxial)
  • 2 x USB and 1 x FireWire
  • 2 x USB and 1 x RJ-45 (Gigabit Ethernet)
  • 5 x Analog Audio (Mic-In, Line-In, Front, Center/Sub, Rear) and S/PDIF-OUT TosLink.

Package Contents

We had no opportunity to describe the package contents, as we had an engineering sample. According to the information on the official web site, the model will come shipped with necessary documentation, ATA66 cable (1), FDD cable (1), SATA cables (8) with power converters (for 4 devices), some front panel module with USB and GigaWire ports and audio jacks, a rear panel bracket with GigaWire and USB ports, rear I/O shield, floppies with drivers for both SATA RAID controllers, CD and DVD with necessary drivers and software.

Integrated Controllers

  • Audio, based on the HDA codec SigmaTel STAC9221 supporting 7.1 surround sound audio with front line-in/out and S/PDIF-Out jacks
  • Network, based on Intel 82573V chip, 10/100/1000 Mbit/sec (PCI-E Gigabit Ethernet)
  • SATA RAID controller, based on Silicon Image 3114 chip, supporting 4 SATA150 devices that can form RAID 0, 1, and 0+1
  • FireWire(IEEE 1394a)/GigaWire(IEEE 1394b) controller, based on Texas Instruments TSB82AA2/TSB81BA3 chips, supporting one FireWire port (on the rear panel) and two GigaWire ports (on the bracket plugged to the on-board connectors).

The integrated audio quality was tested in 16bit, 44 kHz using the RightMark Audio Analyzer 5.5 test application and the Terratec DMX 6fire sound card:

Frequency response (from 40 Hz to 15 kHz), dB:
+0.36, -0.10
Noise level, dB (A):
Dynamic range, dB (A):
THD, %:
Very good
Intermodulation, %:
Very good
Channel crosstalk, dB:
IMD at 10 kHz, %:
Very good

General performance: Very good (details). SigmaTel STAC9221 possesses good characteristics (SNR 105 dBA), being one of the best audio codecs among those used in integrated solutions. Objective test results confirm that Intel D955XBK outperforms the majority of available models on the market as far as the integrated audio quality is concerned, though it's not an absolute leader.


Jumpers and switches Configuration jumper Normal/Config/BIOS Recovery
In BIOS v6.00PG from Intel Memory timings + CAS Latency, RAS to CAS Delay, RAS Precharge, Precharge Delay
Memory frequency selection + Auto, 333, 400, 533, 667, 800 MHz
Peripheral bus frequency control + PCI-E=101.32—109.24 MHz at 1.32 MHz steps
PCI IRQ manual assignment -  
FSB frequency setup + ±10%
CPU multiplier +  
CPU core voltage control +  
Memory voltage control + Default, 1.8, 1.9, 2.0, 2.08 V
Chipset voltage control + 1.525—1.725 V at 0.125V steps
PCI-E bus voltage control -  

We used BIOS BK95510J.86A.1452, the latest available BIOS version at the time of our tests. The mentioned BIOS parameters are available in this version, but the viability of non-standard settings hasn't been tested. There is a boot menu function, which allows to select a device to boot from without modifying BIOS settings.

Test notes

Unfortunately, there were some annoying imbroglios, though that could probably happen because we tested an engineering sample (the first product on this new chipset).

  • First of all we were shocked to learn that this motherboard did not detect well Intel processors! It was all OK, when we installed Pentium Extreme Edition 840 (the motherboard identified the processor and set all parameters correctly); but it had problems with Pentium 4 Extreme Edition 3.73 GHz: the board detected it as Pentium 4 Extreme Edition 3.73 GHz and even reported that the FSB frequency must be set to 1066 MHz, but then… it just set its FSB to 800 MHz! Fortunately, after some mysterious "voodoo dances" and forcing all power management features disabled in BIOS Setup, this motherboard condescended to setting the FSB frequency correctly.
  • Secondly, Intel traditionally allows to enter BIOS Setup with a full list of settings only after an on-board jumper is set to a certain position. Now this scheme is updated: when you rearrange the jumper, BIOS resets its settings; while the old modifications prompted to power off and to return the jumper to the default position after you applied changes in BIOS Setup, this motherboard just reboots without any prompts. In the startup process the board detects that the jumper is still in the Configure position… and, right you are, it again resets all your settings! Thus, saving your BIOS settings becomes far from traditional: (1) enter BIOS Setup, having properly set the jumper; (2) change all necessary parameters; (3) save your BIOS settings (fortunately, this option is still present in the menu!); (4) exit BIOS Setup (you can exit without saving changes, as the BIOS settings will be reset to defaults anyway); (5) power off your computer; (6) return the jumper to the default position; (7) power up the computer; (8) enter partial BIOS Setup by pressing the F2 button; (9) load your settings; (10) and finally exit with saving changes. Doesn't it look like "voodoo staff"? That seems very much like it…
  • Thirdly, for some unknown reason the motherboard refused to work with KVM (Keyboard-Video-Mouse) switch, which we use in our testbeds to save the room and resources. In case of Intel D955XBK, Windows couldn't detect a mouse connected via a KVM switch (none of the previously tested motherboards had such problems). And when we plugged a mouse to the testbed, the system lost the keyboard connected via KVM! Formally, the manufacturer does not claim that it's compatible with KVM switches, but considering the "complexity" of such devices and the lack of problems with that in other motherboards…

Let's hope that production-line samples of D955XBK will have the above mentioned drawbacks fixed, especially as even the last problem can be most likely corrected in BIOS.

This model on the manufacturer's web site (Russian mirror)

The motherboard is kindly provided by the manufacturer

Vladimir Senchihin (sench@ixbt.com)
June 28, 2005.

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