Aopen AP59S Motherboard Evaluation

General Impressions

AOpen has produced another high quality motherboard, and has exploited the features of the SiS5591 chipset very well. Unfortunately, it does not stand up well against the R581A in regards to expandability. The limited number of card slots and memory slots makes this board less desireable, though it has a much wider range of voltage settings than the R581A. Lack of an ATX power connector completes the major list of limitations.

While we are very impressed with the stability of the motherboard, as well as the wide range of voltages, bus speeds and multipliers, we feel that it comes in a close 2nd place among the motherboards with the SiS 5591 chipset.


AOpen decided to use DIP switches for setting the clock multiplier and voltages, which makes for very easy configuration. The voltage can be set from 1.3v through 2.05v in .05v increments, then from 2.0v through 3.5v in .5v increments. Obviously, AOpen is thinking ahead to .18 micron processors with this implementation. The clock multipliers supported are 1.5x to 5.0x in .5x increments.

The bus speed is set with a jumper and includes 60, 66, 75, 83, 90 and 100MHz. Unfortunately, like the other SiS5591 chipset boards available today, the 100MHz bus setting does not work with any current processors – including the K6-300. Both the PCI and AGP bus speeds are asynchronous at system speeds above 66MHz, with the exception of one 75MHz setting, which runs them both synchronously (37.5/75). We found that the motherboard ran at 90MHz without any problems.

The major limitations of this board are the number of card and memory slots. Only 2 ISA slots are included, though both will accept full length cards. There are also 3 PCI slots and 1 AGP slot. The only saving grace for this configuration is that none of the slots are shared. AOpen also elected to include only 2 DIMM and 2 SIMM slots, though all of them can be filled with EDO memory up to a maximum of 768MB. With only 512k cache, however, the chipset will only cache up to 128MB of memory.

The performance of the board is decent, though not quite up to the R581A, due to the difference in cache size. It seems that AOpen was attempting to produce an inexpensive motherboard to compete with other manufacturers products by using a relatively small PCB (8.6″ x 9.5″), 512k cache and fewer slots. AOpen is usually a bit more expensive than offerings from other manufacturers due to their quality design, components and support. Unfortunately, end users rarely consider these aspects when purchasing a board, thus requiring the manufacturer to try to cut costs in other ways.

Cool and/or Unique Features

This board introduces a resetable fuse for the keyboard and USB connectors! One of the most irritating legacies from the past has been the keyboard fuse, which can render an otherwise perfectly good motherboard inoperable. This feature should reduce the number of problems in this area to almost zero, and give users a much more durable motherboard

The BIOS has multi-language support, which can be implemented by downloading the correct BIOS version from AOpen’s website. The BIOS will then display it’s messages and screens in the language of your choice. Just another example of the customer oriented attitude of AOpen.


The 2 ISA/3 PCI configuration is somewhat disappointing, though they did at least avoid putting any shared slots onboard. They also decided to put the IDE connectors between the ISA and PCI slots, which is a rather interesting configuration. The potential problem here is that some IDE cables may have problems having to stretch over the PCI cards, and will make it more difficult to install and remove cards.

Except for those problems, AOpen has used the board real estate fairly well. The DIP switches are directly in front of the ISA slots, for easy access, though the bus speed jumpers are potentially right under the drive bays. The CPU socket and memory slots are out of the way of any obstructions, which makes them relatively easy to get to without removing the board or other components.

Compatibility & Stability

All processors we tested worked well on this motherboard at their rated speed. The IDT C6-225 chip was recognized without problem, as was the K6-300. Though there is a 100MHz bus speed setting, we could only get the board to boot at 90MHz with any CPU. At that bus speed, we found no stability problems at all, even with standard SDRAM. We tested several brands of SDRAM, including Micron PC100 SDRAM, without any problems at all. We also tested EDO and FPM modules, which worked as well.

As with all recent AOpen offerings, the board showed very good stability at any of the working bus speeds, and did not exhibit any compatibility problems with the hardware we were able to test it with. For those simply looking for a solid, reliable product you will find it in this motherboard.


The included manual is well written, and includes explanations for several of their optional utilities and features. They have also included the, now standard, Norton Anti-Virus CD which includes drivers and utilities as well.


Had the AP59S been introduced before the R581A, we would have picked this board as the best SiS5591 chipset motherboard, as it is a bit better than the Gigabyte GA586SG. Unfortunately, the smaller cache size and card/memory slot limitations prevent this board from being a better buy than the M Tech offering. On the other hand, for those who appreciate AOpen’s quality and support, and who want to watch their pocketbook this is a dependable, quality product

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