The good stuff
Most of the Tiger MPX's merits will be obvious to those of you familiar with the Tiger MP. This is one of a handful of motherboards capable of delivering AMD multiprocessing for a desktop system. As such, the Tiger MPX is endowed with all the goodness of AMD's multiprocessor systems.

Many of those advantages are conferred by AMD's 760MPX chipset, which consists of the AMD 762 north bridge chip and the 768 south bridge chip. The 760MPX differs from AMD's original 760MP chipset only in the south bridge chip; the 762 north bridge is unchanged.

The key features of AMD multiprocessor systems—most of which are provided by the 762 north bridge—make this platform very potent, so we'll review 'em:

• Dual front-side busses — Unlike Intel's multiprocessor systems, AMD's multiprocessor systems give each CPU its own, dedicated front-side bus. A shared front-side bus has been a bottleneck in traditional desktop SMP systems, especially in Pentium III systems where the FSB only offers 1.06GB/s of bandwidth. The 762's dual busses each offer 2.1GB/s of bandwidth per processor. Not only that, but Athlon systems use the EV6 bus protocol, borrowed from the (DEC-then-Compaq-then-Intel) Alpha, which is a bit more advanced in some respects than the GTL+ bus used in the Pentium III and Pentium 4. (Not that Pentium 4-based Xeons, with their 400MHz FSBs, are exactly hurting for bus bandwidth.)

• Cache coherency — Athlon MP systems use a protocol called MOESI to manage data in the processors' data caches. This mechanism, combined with the 762 north bridge, allows either processor in the system to fetch data stored in the other processor's cache without first transferring that data into main memory. Instead, if CPU 1 wants to grab some data stored in CPU 2's cache, it will request the data, and CPU2 will pass this data through the 762 memory controller and into CPU 1's cache. Managing cached data in this way ought to offer much improved performance.

• DDR SDRAM — AMD first brought DDR to the mainstream with the 760 chipset, and a dual-processor system is the perfect place to take advantage of the extra memory bandwidth DDR brings.

Don't underestimate the potency of this combination of features. Implementing these things in any platform is by no means trivial, and the fact AMD and Tyan can deliver them on the desktop (or in low-to-mid-range server and workstations) is exceptional.

Face it, SMP on the desktop hasn't exactly set the world on fire. Enthusiasts toyed with SMP Celeron rigs back in the day with BP6 motherboards and the like, but generally, the price premium hasn't brought enough performance along with it. Folks soon discovered that, for a variety of reasons, two processors don't usually perform anywhere near twice as fast as one. But with dual FSBs, superior cache management, and more memory bandwidth, AMD's dually systems eliminate some of the key roadblocks to SMP performance.

Pant, pant.

The 768 south bridge chip in the 760MPX chipset adds a few new features to this mix. Among them:

• A 64-bit, 66MHz PCI bus — The 760MPX now has a 66MHz PCI bus, so it can accommodate high-end PCI cards for server applications where regular old PCI won't cut it—things like SCSI RAID controllers and Gigabit Ethernet NICs. With 533MB/s of bandwidth, 64-bit/66MHz PCI quadruples the available bandwidth over the usual 32-bit/33MHz standard. The 760MP, by contrast, offered 64-bit PCI, but only at 33MHz for peak bandwidth of 266MB/s.

• A faster north-south bridge interconnect — Like many previous-gen desktop chipsets (think KT133 or Intel BX), the 760MP used the shared 32-bit/33MHz PCI bus for communication between north and south bridge chips. The 760MPX still uses the shared PCI bus, but it does so at 64 bits and 66MHz. As a consequence, the north-south bridge link jumps from 133MB/s to 533MB/s.

  The 762 chip has always been capable of sitting on a faster PCI bus, but the 766 south bridge chip in the 760MP chipset wasn't. The 768 chip enables the faster interconnect.

• A secondary 32-bit, 33MHz PCI bus — Since 66MHz PCI slots aren't compatible with the vast majority of expansion cards out there, the 768 chip also integrates a traditional 32-bit/33MHz PCI bus. On the Tiger MPX, four of the six PCI slots are 32-bit/33MHz slots.

• AC'97 audio — Although the Tiger MPX doesn't take advantage of it, the 768 chip now incorporates an AC'97-compatible audio controller capable of powering on-board audio.