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SiS's 648 chipset

Little SiS brings big things to the Pentium 4

TODAY SIS IS OFFICIALLY letting loose its new 648 chipset for the Pentium 4, and we're welcoming it by testing the 648 against six of its closest competitors in a total of 11 different configurations.

Yes, our skin is pasty white, and sunlight hurts our eyes.

But you get to benefit! We'll show you just how this new chipset contender, which packs a wallop with AGP 8X and unofficial DDR400 support, stacks up.

Introducing the 648 chipset
The 648 chipset has nearly every one of the latest features you might want in a new chipset. The 648 north bridge chip has a revamped AGP interface with AGP 8X support and—surprise!—twice the bandwidth of AGP 4X solutions. The front-side bus supports the latest Pentium 4 chips with 533MHz bus speeds. And the reworked memory controller is faster than in the 645/645DX chipsets, with the ability to host three DIMMs of DDR266 memory or two DIMMs of DDR333. Unofficially, the 648 will support DDR400, as well—the necessary bus-to-memory clock ratio is there, and it worked flawlessly in our tests with a single stick of Corsair DDR400 memory. (When the time comes, I expect SiS to release a "648DX" chip that's unchanged in silicon but has official support for DDR400.)

The 648 north bridge chip

In between the 648 north bridge and the new 963 south bridge chip is SiS's proprietary MuTIOL chipset interconnect. This 16-bit interconnect runs at an effective rate of 533MHz, delivering a total of 1GB/s of bandwidth. That's twice the speed of VIA's "Enhanced V-Link" and four times as fast as Intel's Accelerated Hub interconnect.

Source: SiS

The extra bandwidth will be needed, because SiS's new 963 south bridge chip can push a whole lotta bits at once. The chip supports up to six USB 2.0 ports at 480Mbps a pop, plus three IEEE 1394a (also known as Firewire) ports at 400Mbps each. The 963's updated disk controller can support dual ATA/133 channels, as well. Like its predecessors, the 963 also supports the full range of south bridge three-letter acronyms, including PCI, LPC, and ACR. The PCI controller can sustain six PCI master devices at once.

The 963 south bridge chip handles I/O duties

The AC'97 audio built into SiS's 735/745 chips for the Athlon sounded much cleaner to my ear than, say, VIA's south bridge audio. This time out, SiS has added more AC'97 channels, so the 963 can support six channels of audio plus a V.90 modem. (Yep, AC'97 is also used in chipsets for modem support.) As a result, the 963 can drive 5.1-channel surround audio speaker systems, if mobo makers choose to implement all six channels of SiS AC'97 sound.

All told, these feature additions and updates give the 648 chipset nearly every cutting-edge feature one could imagine, with a few possible exceptions like Serial ATA. In short, the 648 is loaded.