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VIA's P4X333 chipset


533 + 333 = Mmmmm
— 12:25 AM on May 15, 2002

REMEMBER WHEN THE PENTIUM 4 was new? It had sort of a rough childhood, getting beat up routinely by its older brother, not to mention that AMD bully down the street. Lately, though, we've seen the Pentium 4 come into its own. Once it shed its 0.18-micron skin and its cache grew out, it turned into quite the contender.

Of course, it had help from parent Intel on that front. From the 845 with DDR support to last week's introduction of the 850E with its 133MHz bus support, Intel has done a good job of making sure that the Pentium 4's NetBurst architecture has been well fed.

Not that Intel is alone in this endeavor. In fact, Intel has more help than it even wants. Rival chipset maker VIA has, in spite of a lawsuit between the two companies over rights to the P4 bus, produced its own chipsets for the Pentium 4. First was the P4X266, with support for DDR SDRAM at a time when Intel's own chipsets supported only RDRAM or PC133 SDRAM. Next came the P4X266A, featuring greater performance thanks to an improved memory controller and ATA/133 support. Now, we look at VIA's third Pentium 4 chipset, and the third time really is the charm. The new chipset supports a 533MHz bus and DDR333 SDRAM, and that's just the tip of the iceberg. Let's take a closer look at VIA's P4X333.

What's new with you?
In the case of the P4X333 chipset, quite a bit is new. It's obvious from the aforementioned new features that VIA has changed the north bridge to add support for DDR333 memory. What is less obvious, but also very important, is an all-new south bridge chip, as well as a new link between the north and south bridges. Both of the chips that make up the P4X333 chipset are pin-compatible with their older counterparts, so updating a P4X266A motherboard to support the new chipset should be a trivial matter.


VIA's all-new south bridge chip

There are enough new features in the P4X333 north bridge and the VT8235 south bridge that the easiest way to look at them is on a point by point basis:

  • 533MHz bus support: As mentioned before, the P4X333 adds official support for a 533MHz bus speed. Our test of the Intel 850E showed that the Pentium 4 can certainly take advantage of the higher bus speed with RDRAM; it will be interesting to see what improvement is provided with DDR.

  • DDR333 SDRAM support: To help keep the 533MHz bus nice and full, the P4X333 also adds support for DDR333 SDRAM. This change raises the peak theoretical memory bandwidth from 2.1GB/s to 2.66GB/s. This pulls DDR's theoretical peak bandwidth closer to the theoretical 3.2GB/s peak of PC800 RDRAM. Not only that, but VIA has improved the P4X333's memory controller over the one found in its KT333 chipset in order to wring out even more performance.

  • Enhanced V-Link: Previous VIA north and south bridges were connected by V-Link, an 8-bit wide, 66MHz quad-pumped bus good for 266MB/s of bandwidth. The P4X333 doubles the clock speed on the bus to 133MHz, doubling the bandwidth to 533MB/s.

  • AGP 8X: The P4X333 is the first VIA chipset to support AGP 8X, which doubles the effective transfer rate of AGP 4X, at least in theory. Obviously, this feature is a little ahead of its time, but it will certainly be appreciated once 8X AGP cards begin to hit the market in force. The P4X333's AGP controller is (of course) backward compatible with older AGP implementations such as AGP 4X.

  • ATA-133: The VT8235 South bridge includes ATA-133 support for all IDE devices. If the drive supports it, ATA-133 can improve performance by allowing for higher hard drive burst speeds.

  • USB 2.0: The VT8235 also incorporates three USB 2.0 root hubs supporting six ports. USB 2.0 is a vast improvement over USB 1.1, raising the bandwidth from 12Mbps to 480Mbps. The incorporation of USB 2.0 into chipsets like the P4X333 should speed the widespread adoption of USB 2.0 devices.

  • A redesigned PCI bus: In addition to the aforementioned new features, the VT8235 has a completely redesigned PCI implementation. Hopefully, this reworked PCI implemenation will eliminate the nagging PCI issues VIA users have experienced in the past with video capture devices and RAID cards.


A block diagram of the P4X333 chipset (Source: VIA)

As you can see, the new chipset makes the P4X266-to-P4X266A update look pretty minor in comparison. VIA has not only added the latest performance goodies in the form of the 533MHz bus and the DDR333 support, it's also prepared the P4X333 for the future, with forward-looking features like AGP 8X and USB 2.0. Now that we've got an idea of what this thing is capable of on paper, let's get to the benchmarking and see how it does in the real world.