The competition
Chipset support for AMD products has never been better, so the KT333 faces stiff competition. We've limited our comparison to DDR-capable chipsets only, which narrows the field a bit, but we still have seven different competitors lined up. Here's a quick glance at how they measure up in terms of vital specs, including north bridge features and the link to the south bridge.

AMD 760 NVIDIA nForce 420D SiS 735 SiS 745 VIA KT266 VIA KT266A VIA KT333
Memory types
(DDR only listed)		 PC1600 (200)/ PC2100 (266) DDR SDRAM PC1600 (200)/ PC2100 (266) DDR SDRAM PC1600 (200)/ PC2100 (266) DDR SDRAM PC1600 (200)/ PC2100 (266)/ PC2700 (333) DDR SDRAM PC1600 (200)/ PC2100 (266) DDR SDRAM PC1600 (200)/ PC2100 (266) DDR SDRAM PC1600 (200)/ PC2100 (266)/ PC2700 (333) DDR SDRAM
Max. effective memory clock speed 266MHz 266MHz 266MHz 333MHz 266MHz 266MHz 333MHz
Memory bus width 64 bits 2 * 64 bits 64 bits 64 bits 64 bits 64 bits 64 bits
Peak theoretical memory bandwidth 2.1GB/s 4.2GB/s 2.1GB/s 2.66GB/s 2.1GB/s 2.1GB/s 2.66GB/s
Maximum addressable RAM 4GB 1.5GB 1.5GB 3GB 4GB 4GB 4GB
North/south bridge interconnect PCI Hyper- Transport MuTIOL MuTIOL V-Link V-Link V-Link
Interconnect clock speed 33MHz 400MHz 33MHz 33MHz 266MHz 266MHz 266MHz
Interconnect bus width 32 bits 8 bits * 2 8 * 32 bits 8 * 32 bits 8 bits 8 bits 8 bits
Peak theoretical interconnect bandwidth 133MB/s 800MB/s 1.06GB/s 1.06GB/s 266MB/s 266MB/s 266MB/s

The specs on many of these chipsets are very similar, as core logic chipsets tend to be. The older AMD and VIA chipsets are, of course, familiar by now. However, there are a couple of stand-outs that look to challenge the KT333, and we've not reviewed either of them, so I'll take a second to introduce them.

Pretty sneaky, SiS
SiS's 745 chipset is an updated version of its older 735 chipset. The update adds—you guessed it—support for DDR333 memory. The 735 and 745 are interesting for a number of reasons, however. Among them:

  • Single-chip design — Yep, this isn't really a "chipset" so much as one chip that integrates the functionality of traditional north and south bridge chips. This innovative approach to chipset design offers a number of advantages, including the possibility of making some very low-cost, high-performance motherboards.

  • MuTIOL madness — The fact everything resides on a single chip has allowed SiS to created the single fastest north-south bridge link anywhere. SiS's "Multi-Threaded IO Link", or MuTIOL for short and confusing, employs eight different 32-bit, 33MHz channels for a total of 1.06GB/s of bandwidth.
On paper, the 735 put SiS near the top of the heap in Socket A chipsets. Likewise, the 745 was the first Socket A chipset available with DDR333 support; we purchased the board we tested from an online vendor. Sadly, the 735 and 745 haven't exactly been widespread successes. As far as I know, only ECS and Leadtek make SiS 735-based boards, and only ECS sells a 745 mobo. ECS mobos are fairly solid and very cheap, but they don't exactly light up the sky with snazzy features. Still, these SiS chip "sets" are intriguing.

NVIDIA's formidable nForce
NVIDIA's nForce 420D sports some of the niftiest features of any core logic chipset, so it can't be ignored. Among the highlights:

  • Dual banks of DDR266 memory — The nForce supports two separate banks of PC2100 memory, so its peak memory bandwidth capacity is 4.2GB/s. On paper, that's well more than the DDR333 chipsets can deliver.

  • Hardware prefetch — To better use those dual memory banks, the nForce incorporates in its memory controller the ability to fetch and cache data the CPU is likely to need soon. NVIDIA calls this feature DASP, for Dynamic, Adaptive, Speculative Pre-processor. Because the Athlon XP processor includes its own hardware prefetch logic that works quite well, DASP seems a little bit redundant, but you've gotta like the idea.

  • AMD's HyperTransport — The interconnect between north and south bridges uses AMD's next-gen I/O link spec, HyperTransport. In the nForce, HT delivers 800MB/s of bandwidth, which makes it easily the fastest chip-to-chip interconnect of the bunch. (SiS's on-chip stuff doesn't count.)

  • Really good audio — The nForce's Audio Processing Unit (APU) is lifted from the Xbox, as are many other bits in the nForce. That's a good thing, because Xbox audio is quite good. The APU supports up to 256 simultaneous audio streams and true Dolby Digital 5.1 audio.

  • Integrated NVIDIA graphics — Claiming to have the best integrated graphics in the chipset world is a little like claming to have the best tasting dog food around. You may well be right, but I'm not gonna eat it. Still, this is NVIDIA we're talking about, and the nForce has a GeForce2 MX-class IGP, or Integrated Graphics Processor, on board. We'd rather keep our GeForce3 Ti 500, and since most nForce boards include a separate AGP slot, that won't be a problem.
Many folks expected nForce to take the market by storm when it arrived, but that hasn't exactly happened. The combination of high costs and tough competition from VIA's KT266A has kept the nForce from gathering much momentum. However, NVIDIA has a lower-cost version of the nForce coming, the 415D, which does away with the on-board graphics. Perhaps 415D will make a little more headway in the market.