For years users that were interested in multiprocessor systems were instructed to go one of two routes, Supermicro or Tyan.  For any high-end server system based on an Intel processor it was either Supermicro or Tyan.  However in recent times more and more motherboard manufacturers are finally beginning to complete their product lines with a true high-end offering.   ASUS was one of the first to start the trend with their multiprocessor Pentium Pro/II boards, and at last year's Fall Comdex both ABIT and AOpen (two companies that consistently bump heads in the industry as competitors) announced Dual Processor Pentium II boards for the higher end of the performance spectrum.

Epox is the latest manufacturer to join the club of dual processor Pentium II boards, as they combine the excellence of their motherboard design with the multiprocessor NT/Linux environment that the Pentium II seems to fair quite well under.  The result is the Epox BXB-S, finally, a dual processor Pentium II board without an incredible layout problem and an overall quality rarely seen in this special market.

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Motherboard Specifications

CPU Interface Dual Slot-1
Chipset Intel 440BX
L2 Cache N/A (on-chip)
Form Factor ATX
Bus Speeds 66 68 / 75 / 83
100 / 103 / 112 / 133
Clock Multipliers 3.0x - 5.0x
Voltages Supported 2.0v / 2.8v (Auto Detect)
Memory Slots 4 168pin DIMM Slots
Expansion Slots 1 AGP Slot
4 PCI Slots (4 Full Length)
2 ISA Slots (0 Shared / 3 Full Length)

The Good

If you look over the specs on the EP-BXB-S there is one thing that should stand out at first, and that is the expansion slot configuration, 4/2/1 (PCI/ISA/AGP).  What's so special about having 4 PCI and 2 ISA slots?  The fact that on the BXB-S, none of the PCI or ISA slots are shared, meaning all 7 on-board slots can be occupied at once unlike other motherboards that either feature a 5/2/1 or a 4/3/1 configuration which sacrifice either one PCI or one ISA slot in order for all 7 slots to be filled.  Since the 4/2/1 configuration of the BXB-S is non-shared expansion slot configuration, the expandability of the board is equivalent to that of a 5/2/1 board when using 2 ISA expansion cards.  A unique approach to the relatively uncharted dual processor market, and an eye catching one at that. 
All of the four PCI slots are PCI Master slots and the adjustable IRQ assignments in the BIOS of the BXB-S does its best to eliminate of peripheral conflicts before they have to be dealt with by the user.  A plus for any server motherboard, when it comes to building a server, you usually don't want to have to deal with the hassles of IRQ conflict resolution, you'll already have enough to deal with as a server admin.  Take AnandTech's word for it ;)

Two processors for twice the fun...from Epox

The reason for only including 4 PCI slots is to prevent any possible conflicts with the on-board PCI SCSI Ultra2 controller by Adaptec, more specifically the 7890 PCI-to-Ultra2 SCSI controller.  By including the SCSI device on-board you are not truly limiting your expansion as the rate of change in the SCSI disk market is relatively slow, comparatively speaking to say the rate of change in the processor or video card industry.  Even most newer servers built on motherboards like the BXB-S don't even take use of the Ultra2 (80MB/s) capabilities and simply use Ultra Wide SCSI-3 compliant devices (40MB/s) which the controller also supports. 

The interface ports for the on-board SCSI controller are carefully placed on the extremely well laid out motherboard.  The Ultra2 SCSI LVD (Low Voltage Differential) port is located south of the empty space between the last ISA slot and the first PCI slot, making sure not to block the path of any full length ISA or PCI cards that may be installed in the motherboard.  Far away from the Ultra2 LVD connector, towards the lower right hand corner of the motherboard is the 68-pin Ultra Wide SCSI interface which is directly below the 50-pin Ultra SCSI connector.   The 68-pin Ultra2 interface is on a channel of its own while the 68-pin Ultra Wide and the 50-pin Ultra connectors are on a separate channel, to prevent any one Ultra Wide or Ultra SCSI device from decreasing the maximum throughput of any Ultra2 devices you may have in your system from the 80MB/s of performance you paid for with those devices.  In most first generation boards with on-board Ultra2 SCSI the distribution of SCSI channels was a definite problem, however the path Epox has chosen with an independent Ultra2 and an independent Ultra Wide/Narrow channel is the most sensible one, overall.

Strategically positioned out of the way of any full length PCI or AGP cards in the last PCI or AGP slot, the two IDE interface connectors are positioned parallel to the Ultra2 LVD connector and are separated from it by the Adaptec 7890 controller chipset. 

The positioning of the ATX power supply connector is ideal on the already crowded yet well spaced-out BXB-S as it conforms strictly to the ATX specification by locating itself in the lower right hand corner of the motherboard.  Directly above it are the 4 DIMM slots on the motherboard, supporting up to a total of 1GB of RAM if you happen to be using registered 256MB DIMMs.  Epox suggests that 4 clock SDRAM be used instead of 2 clock SDRAM, a requirement that didn't seem to have any difference in AnandTech's tests, however to be on the safe side (as not even a week of non-stop testing is enough to simulate a server environment) you will want to specify 4 clock SDRAM for use with the BXB-S.  Why is there no external DRAM buffer on the BXB-S?  There is no need for one, the trace lengths between the 443BX chip (the larger of the two chips making up the 440BX, the other being the smaller PIIX4e Bus Master IDE controller) and the memory banks are short enough to avoid any capacitance related stability issues.  To further ensure solid operation the BXB-S is healthily populated by mid-sized Sanyo tantalum capacitors, arguably considered to be some of the best in the industry, including a concentration around the memory banks, and between the 443BX chip and the banks as well. 

Of course the BXB-S wouldn't be complete if it weren't for the dual Slot-1 CPU interfaces present on the board, both featuring custom made universal CPU retention kits that unfold instead of forcing you to install the retention kit yourself.  Although that may not be a big deal, it does cut down on the total install time in the end, and a "feel-good" convenience feature of the BXB-S.  A high concentration of those same Sanyo capacitors is present around the two CPU slots as well as between the AGP and PCI slot, and between the two ISA slots; stability is a primary concern for Epox, and it shows. 

The Good (cont.)
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