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TR reviews the Via KT133A chipset

PC133 power

Well, it's been a long time coming, but it's finally here. Our review of Via's KT133A chipset is later to market than a DDR motherboard.


Seriously, folks, the KT133A has been around for a while, and so has the skeleton of this review, on which I've finally found time to put some flesh. Heck, my own computer has been running on a KT133A motherboard for a while now, come to think of it. And we just published a review of a KT133A mobo, the Abit KT7A-RAID. So I darn well ought to have published this review already, instead of running around in DDR land.

Thing is, even though DDR chipsets and motherboards are finally starting to hit the market in earnest, the KT133A is increasingly looking like it's going to be around for a while. Read on to find out why.

Before we go much further, though, I should stop and point out that the Asus AV7133 motherboard we used for this review was provided by TR's excellent hardware sponsors, Dr. John and the gang at KickAss Gear. If you happen to decide you want to buy a KT133A based mobo, you couldn't do much better than to pick up an A7V133 from the folks at KickAss Gear. As KT133A boards go, it's the best.

What you're getting
The KT133A chipset is essentially the Via KT133 chipset, only tweaked to support a 266MHz front-side bus (FSB) clock frequency. That is, a 133MHz FSB that sends data twice per clock, actually.

We like to mix it up to keep a little confusion going.

But there is a little more to the KT133A than that. For one thing, the VT8363A north bridge chip—the one modified to support the faster bus, and the real heart of the chipset—has been widely reported to handle bus speeds quite a bit higher than the official 133/266MHz spec. KT133A north bridge chips manufactured very late last year or in 2001 have hit speeds of 150MHz and above. That's a big deal, because previous Athlon chipsets just weren't friendly to bus overclocking. Since KT133A motherboards are, most often, slightly revised versions of KT133 boards, they're mature products, and many offer robust, menu-driven overclocking options. Taken together, these things could add up to one seriously fast Athlon platform for the overclockers among us.

Way back when, most manufacturers chose to pair the KT133 north bridge chip with Via's VT82C686A south bridge, which was the official KT133 south bridge chip. (Via offers several south bridge chips that communicate with the north bridge using the PCI bus, so they're interchangeable.) Via has since revised the 686 south bridge chip to support newer, ATA-100 storage devices. Most KT133A boards now ship with the new 686B revision of this chip.

A typical PC system configuration using the 686B south bridge

Beyond that, the KT133A still includes all the features that have made the KT133 the most popular Athlon chipset around.

But there are a few things the KT133A can't do, and we'd best recount those. For one, the KT133 chipset doesn't support DDR SDRAM. (DDR memory support is coming from Via in the form of the KT266 chipset, which we'll be reviewing soon. The KT266 is much like its Pentium III-oriented sibling, the Pro 266.) DDR memory promises double the bandwidth of conventional SDRAM at a small price premium, but it's been much slower to market than anticipated. Also, DDR DIMM prices have only recently begun to drop to reasonable levels, while PC133 SDRAM is exquisitely cheap. We'll be testing the KT133A against AMD's 760 chipset, which support DDR SDRAM, to see whether the price premium is worth it.

Also, the KT133A still links the north and south bridge chips via the PCI bus. All of Intel's 800-series chipsets and Via's newer chipsets, the Pro 266 and KT266, use a decicated, low-latency interconnect with 266MB/second of bandwidth—twice that of the PCI bus, and the PCI bus isn't a dedicated link. In theory, the KT133A will be at a comparative disadvantage in certain scenarios where the system has to move large amounts of data from several sources and destinations at the same time. However, the KT133A's main competitor at present is AMD's 760 chipset, which also uses the PCI bus to link the north and south bridges.