AOpen AK72 KX133 Slot-A ATXby Anand Lal Shimpi on March 21, 2000 1:05 AM EST
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VIA recommends that their 686A Super South Bridge be used in combination with the 371 North Bridge on all KX133 designs, so AOpen decided to abide by the design guide and outfitted the AK72 with the 686A Super South Bridge. The benefits of doing this seem kind of silly when you consider the fact that the AK72 features such a large PCB. The 686A helps to reduce the overall cost of the motherboard by integrating hardware monitoring functionality, an ISA bridge, as well as the basic I/O controller functions into a single South Bridge chip.
The overall cost of the motherboard is reduced because the manufacturer doesn't have to use external chips for all of these functions that not only add to the cost of the board but also occupy PCB space on the board which causes the board to be larger and thus cost more. But in the case of the AK72, AOpen had more than enough room on the board for space constraints not to be a major issue. In this case the 686A is still a more cost effective alternative to the 596B South Bridge that doesn't boast the same high levels of integration, but AOpen's design negates some of the benefits of using this particular chip.
The 686A also provides support for a total of 4 USB ports, unfortunately AOpen failed to provide an external USB header for the remaining two ports supported by the chip.
Things get even more odd when you look at the AK72's expansion slot layout. The board itself features a 5/1/1/1 (PCI/AGP/ISA/AMR) expansion slot configuration, but the slots themselves are laid out in a manner that once again, doesn't make optimal use of the space on the board. Instead of sharing the AMR slot with a PCI slot so that it would not occupy the space required for another slot on the motherboard, AOpen chose to stick the AMR slot at the end of the board where it occupies the space that could have been used to provide for a sixth PCI slot. The AK72 covers all ends in terms of expansion, and all of the slots are capable of accepting full length cards which is one of the very few benefits of the AK72's larger PCB design.
The AMR slot on the board is driven by Analog Devices' AD1881 codec which is a very popular chip among motherboard manufacturers. The sound quality is ok, but you can't really expect all that much more from a software driven audio codec. Most users will want to go with their own hardware PCI sound solutions.
In accordance with the usual AOpen style, the Slot-A interface is surrounded by six hefty heatsinks that are mounted on the switching voltage regulators by the connector as well as 14 2200uF capacitors. These 14 capacitors are the same low ESR (equivalent series resistance) capacitors from the AX6BC Pro Gold and AX6BC Pro Gold II Millennium Edition that supposedly allow for increased stability. Whether these low ESR capacitors actually improve stability is up to you to decide, AOpen was just as stable before they started using low ESR caps as they are now with the new caps.
The AK72 features AOpen's jumperless CPU setup utility that is located within the AWARD 6.00PG BIOS setup on the board. While the utility obviously doesn't allow for the manual adjustment of the Athlon's clock multiplier (that is left up to external overclocking devices) it does allow for the manual adjustment of the processor's core voltage in 0.05v increments and lets you choose the 110 and 115MHz overclocked FSB settings. From our tests in the past, we have yet to encounter an Athlon motherboard that could even so much as boot at a FSB frequency setting much greater than 110MHz. While there have been some success stories for the most part, 110MHz is about the maximum FSB frequency you can expect to attain on a current or previous generation Athlon motherboard.
It is very welcoming to see the return of AOpen's high quality written documentation in the form of the AK72's User's Guide which is a comprehensive manual that describes the features of the board as well as in the form of an Easy Installation Guide poster that guides you through the setup of your AK72 based system. For quite some time it seemed like AOpen had ditched the idea of bundling written documentation with their products, but it's good to see that they have elected to include some pretty good documentation with this board that could really come in handy because of the drivers that need to be installed for proper support of the KX133 chipset.