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In our first Socket-478 DDR motherboard review, we take a look at the AOpen AX4B Pro. Note that the AX4B Pro has an older sibling, the AX4BS Pro, which only supports PC-133 SDRAM so be sure you are getting the correct model. Let's take a brief technical overview of the AX4B Pro :

As with all other AOpen motherboards in recent years, the highlights of the AX4B Pro are its packaging, black PCB and hefty size of 12" x 9.5" (HxW). Heeding the hordes of case modders out there, the packaging has a cutout "window", giving a peek at the contents within. The motherboard, cables, documentation and CDs are all encased in a plastic clamshell case with an emblazoned AOpen logo, clearly showing AOpen's intentions to bring attention to their product.

The AX4B Pro is yet another hefty package of electronics from AOpen, which may cause some amount of grief (usually it's removing all 5.25" devices) for end-users with small cases. Component placement is a little deficient this time around, with the main complaint being the placement of the IDE and floppy headers. This arrangement prevents the first 3 PCI slots from accommodating full-length PCI cards. While arguably non-critical for the majority of end users, it would certainly bother those of us with larger cards such as caching RAID controllers.

The DIMM slots are about half an inch above the AGP slot, making DIMM installation/removal a non-issue. On some motherboards such as the ASUS TUA266, it is necessary to first remove the AGP card before installing / removing DIMMs.

AOpen again decided to integrate only 2 USB ports, including an additional header on the board as well as a bracket to provide another 2 USB ports. The second USB header is placed towards the lower-front end of the motherboard to cater to cases having front USB connectors, such as the SkyHawk aluminum line. Standard issue design - the front panel connectors are placed in the lower-left corner of the motherboard, ensuring that the cables do not get in the way of any expansion slots.

It seems with the Socket-478 platform, capacitor placement virtually becomes a non-issue. Even with an entire row of 2200uF capacitors barely half an inch from the mount zone, heatsink/fan units such as the newly released Zalman CNPS6500B have no trouble fitting in.

Intel's highly anticipated i845D chipset is essentially the same chipset as the i845, but with DDR capability allowed to be utilized. Being a two chip solution, it consists of the i82845 MCH (Memory Controller Hub) and the i82801BA ICH2 (I/O Controller Hub). The i82845 MCH supports either PC133, DDR200 or DDR266 memory, as well as asynchronous memory bus and FSB operation for PC133 and DDR266 support. The i82801BA is a carry-over from i850, i815 and i810 chipsets, which accounts for the reason why the feature set of the i845 seems a little dated (as compared to the SiS645); only 2 USB host controllers (4 USB ports) and Ultra ATA-100 support. AOpen opted for a massive silver heatsink to dissipate heat from the MCH. While an active cooling solution would definitely be preferable, the MCH did not get very warm during our evaluations.

As with other AOpen motherboards, the AX4B Pro comes outfitted with a universal AGP slot. A locking mechanism at the end of slot helps secure the AGP card in place. It is basically a small plastic clip, working similarly to that of a DIMM slot by clipping onto the small tab on the AGP card. While it would take quite an amount of force to unseat the AGP card (an amount that would likely have damaged other components more severely), it is a small, but welcome feature.

AOpen is one of the few manufacturers who went above and beyond Intel's specifications to outfit their 845 DDR motherboard with 3 DDR DIMM slots. Although the chipset memory limitation of 2GB still applies, memory expansion is much more convenient as 1GB DDR DIMMs are not easy to come by. For expansion slots, AOpen chose to go with the more OEM oriented 1/5/0/1 (AGP/PCI/ISA/CNR) configuration, something which MSI also decided to do on the MSI 845 Ultra-ARU. Only the last two PCI slots are capable of accommodating full-length cards due to the placement of the IDE and floppy headers.

12 2200uF, 4 1500uF, 6 1100uF, and a bunch of smaller capacitors. 6 voltage regulators sit adjacent to the CPU socket. AOpen utilizes a greater number of lower capacitance low ESR (equivalent series resistance) capacitors. Hence, while the total capacitance may be the same, it is distributed more evenly throughout the motherboard. To further enhance stability, the AX4B Pro was designed with the "Frequency Isolation Wall". This was previously described in our AK77 Plus and AK73 Pro(A) articles, but we'll repeat ourselves here. AOpen attempts to separate the motherboard into regions, where each region is running at similar local frequencies. This serves to minimize signal interference via cross talk which is an unavoidable occurrance in electronic circuits. They also took the pains in calculating the trace lengths and routing to ensure that traces operating at the similar clocks have equivalent lengths, minimizing clock skew.

In the overclocking department, the AX4B Pro is fully jumperless. FSB is adjustable in 1MHz increments via the BIOS, with the clock generator being capable of an astonishing 248MHz! CPU core voltage is similarly jumperless, allowing adjustments from 1.1V to 1.85V in 0.25V increments. Being an Intel CPU, the Pentium 4 is multiplier-locked. VIO and DIMM voltage adjustments are absent. How this will affect the AX4B Pro's overclockability remains to be seen. All 3-pin fan headers held up well when loaded with a black-label Delta fan.

Other than the DFI AK76-SN, every motherboard that passed through our labs had integrated AC'97 audio. AOpen went with the no frills Analog Devices AD1885 CODEC. For casual use, the integrated audio performs acceptably, with processor use not noticeably slowing down the system. However, for more intensive uses, such as DVD playback or gaming, it would definitely be preferable to go with a hardware-based sound card as they generally hog less CPU time while providing more audio functionality and better sound quality.

Another standard feature on AOpen motherboards are the Dr. Voice, Dr. LED and Die-Hard BIOS technologies. Dr. Voice is a diagnostics tool, audibly telling you what is wrong with your motherboard in 4 languages; English, German, Chinese and Japanese. Dr. LED, an optional accessory, is a set of 8 LEDs, which indicate which part of the motherboard might be having problems. Finally, the Die-Hard BIOS technology helps to protect your system from virus attacks or failed BIOS updates. Essentially, there are two BIOS chips on the motherboard, with only the primary chip being active during normal use. Upon corruption of the primary chip's contents, the machine will switch over to the secondary chip. Oddly however, it seems the the second BIOS chip was missing from our evaluation sample.

To complete the package, a product registration card, superb "getting started" poster and 2 CDs are included; one with an electronic version of the manual, the drivers and utilities; the other with a full version of Norton Antivirus 2002 for Win9x/NT/2000/XP. This is a welcome addition, saving the time, money and inconvenience of separately purchasing an antivirus program. The package also contains a detailed manual. So far, AOpen's motherboard manuals describe the product and related technologies / terminologies in detail but lack any descriptions and explanations of the BIOS settings.

Since our last motherboard review, we have updated our test suite. Let's see how the AX4B Pro fares...

For the results below, the AX4B Pro was run with standard parameters (ie. no overclocking) at 1.7GHz (17 x 100 FSB), CAS 2. Please note however, that you shouldn't compare the results obtained here to rate a Socket-A motherboard and vice versa.

In addition to tests using standard parameters, we performed overclocking tests to ascertain the highest FSB speeds the system could sustain. We started by setting the CPU to run at 17 x 100MHz FSB and verified its stability via informal testing. The FSB is gradually increased, and stability is tested using Ultra-X's RAM Stress Test, Stability Test and HotCPU. All tests were done BIOS default memory settings with the CAS latency set to 2.5, to minimize the chances that the RAM was the limiting factor.

While the clock generator on the AX4B Pro is capable of cranking out 248MHz, we reached the stability limit at 128MHz with the processor running at 2.17GHz. This is already pretty good considering the Pentium 4's bus is quad-pumped, ie. a 28MHz FSB increase results in a 112MHz increase.

The good :

• Great aesthetics with the black PCB.

• Massive silver heatsink keeps the MCH sufficiently cool.

• Overclocking is a snap, thanks to the AX4B Pro's fully jumperless implementation. However, there is the lack of VIO and DIMM voltage adjustments, although that didn't stop us from pushing the AX4B Pro to 128MHz

• Stable under standard and overclocked (128MHz FSB) conditions.

• Very user friendly, with clear installation instructions in the form of a "getting started" poster. Additionally, it also has good diagnostic capabilities, with the Die-Hard BIOS and Dr. Voice. The optional Dr. LED should make it even better. Nice software bundle, which includes Norton Antivirus 2001 for Win9x/NT/2000/XP.

...and unfortunately the bad :

• Layout is a little deficient this time around. The only complaint is that the IDE and floppy headers prevent the first 3 PCI slots from accommodating full-length cards.

• Expansion slot configuration of 1/5/0/1 (AGP/PCI/ISA/CNR). Although 5 PCI slots are sufficient for most users, 6 PCI slots would have been even better. While being beneficial to OEMs, the lack of CNR peripherals virtually renders the slot a waste of space.

• Integrated AC'97 audio. While offering acceptable audio quality for casual usage, most users will end up disabling it in favor of a true hardware-based audio solution. Removing the AC'97 CODEC and other associated audio hardware might have reduced the cost of the motherboard.

• Size isn't everything. This thing is a behemoth that might cause problems for those with more compact casings.

Overall, the AX4B Pro is every bit the motherboard most of us would expect from AOpen - a perfectly functional work of art. Fully stable under all our tests, including the rigorous "makeworld -j4" test in FreeBSD 4.5, the AX4B Pro is also no slouch, coming virtually neck and neck with the MSI 845 Ultra. To top these off are the excellent Dr. Voice and Die Hard BIOS technologies, the nice software bundle and excellent documentation. Lastly, there is the sexy black PCB and stylish silver chipset heatsink. However, there are a few chinks in the AX4B Pro's armor. VIO and DIMM voltage adjustments are absent, but fortunately don't seem to  inhibit the its overclockability. While a 1/5/0/1 (AGP/PCI/ISA/CNR) expansion configuration is enough for most users, power users would have preferred to do away with the onboard sound and the CNR slot, replacing it with an additional PCI slot or an ISA slot for legacy support. The first 3 PCI slots are also incapable of accommodating full-length expansion cards due to the IDE and floppy headers. If there was one addition to the AX4B Pro this editor would have liked to see, it would be ATA-133 RAID as in the MSI 845 Ultra. Normally, AOpen produces a Pro and Plus series, however the RAID-equipped Plus version of the AX4B is strangely missing this time around. The AOpen AX4B Pro gets our heartiest recommendations for an i845-based motherboard. Very Highly Recommended!