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Review: VIA PT880

by Tarinder Sandhu on 18 November 2003, 00:00

Tags: Intel (NASDAQ:INTC), VIA Technologies (TPE:2388)

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Chipset analysis

The best way, as always, of understanding the nuances of a new chipset is to look at its block diagram. We know that the PT880 uses twin 64-bit memory controllers to offer up 6.4GB/s of potential bandwidth at 200FSB. We don't know too much more than that right now.



We'll list what we reckon to be the key features in the PT880 design. It's a standard Northbridge / Southbridge configuration with a high-speed interconnect linking the two to one another. We'll start off at the top and work out way down.

PT880 North Bridge

200MHz FSB CPU support - If S478 performance is your aim, Intel's 200MHz FSB (quad-pumped FSB to attain the often quoted 800MHz speed) are the only real way to go. A faster FSB allows the CPUs, compliant Northbridges and system memory to interact at higher speeds. The basic premise is to keep the CPU waiting for the least time possible. Reducing the MHz discrepancy between CPU and the system (the multiplier) is an effective way of increasing performance. Ceteris paribus, a 2.8GHz Pentium 4 800MHz FSB CPU will be faster at most memory-intensive tasks than a 2.8GHz 533MHz processor, assuming DDR400 memory is used.

All 200MHz P4s support the lovely Hyper-Threading technology as standard. Again, this is a method of allowing a single CPU to do more work by making more efficient use of its limited resources. The PT880 support HT technology immediately. It wouldn't have much appeal if it didn't, really.

Dual Channel Memory Support - Along with the faster FSB, dual-channel memory support is a critical factor in raising overall performance. We spoke of the P4's need for 6.4GB/s of potential bandwidth at 200MHz FSB. That's what a dual-channel architecture affords. A traditional 64-bit memory controller, when run with DDR400 memory,outputs 3.2GB/s of bandwidth (200MHz (memory speed) x 2 (signal processing on the rising and falling of each clock cycle) x 64 (bits of the memory controller) / 8 (from bits to bytes)). Add two controllers that work in unison, i.e. 128-bit mode, and you have your 6.4GB/s.

The PT880, much like Intel's i875P Canterwood, also allows for ECC (Error Correction Code) memory and asynchronous memory speed support. The former is necessary if the chipset is to be used in situations where a high degree of reliability is required. The latter is more commonly used to accommodate faster or slower memory, relative to the CPU's FSB.

An interesting feature that's not detailed on the above block diagram supplied by VIA is support for Quad Band Memory. VIA alludes to it in the press kit, but is then not keen to expose its benefits in other literature. Essentially, QBM memory is similar to DDR-II in overall bandwidth output, but it approaches it in a different manner. QBM modules, in very simple terms, would double the present bandwidth from DDR DRAM chips by amalgamating two sets in one package whilst still retaining the standard 184-pin layout. The downside is the increased latency of this approach, and enthusiasts know that latency counts for a great deal when defining a motherboard's performance. For now, we're happy enough with high-speed, low latency memory.

Faster Bridge link - The increasing integration of high-speed functions into an all-in-one South Bridge has put the onus and burden on the interconnect link. Add in, say, multiple USB 2.0 controllers, FireWire support, on-chip Gigabit LAN, native SATA support and you'll appreciate that bandwidth can be chewed up quickly. VIA has doubled the speed of its Bridge V-Link from 533MB/s to 1066MB/s, and it's now knows as the Ultra V-Link. That's getting up towards AMD's HyperTransport speeds.



VT8237 South Bridge

DriveStation - That's the umbrella term used to define just how SATA and PATA figure in VIA's plans. The VT8237 provides on-bridge support for 2 SATA ports that are capable of supporting one drive each in independent mode, RAID0 (striping for performance) and RAID1 (mirroring for security). It also supports the usual 4 PATA devices, split over 2 channels. However, a motherboard manufacturer can take advantage of another 2 SATA ports by incorporating a PHY (physical layer) into its design. That adds the available on-bridge SATA storage to 4 drives and then gives rise to RAID0+1 (striping and mirroring) running. Please note that adding the PHY will take the place of the secondary PATA channel. This, as you will see, is exactly how the reference PT880 is configured.

VIA also attempts to give the user an easy OS-based interface for managing and constructing RAID arrays. The V-RAID DriveThru technology allows one to migrate from a standard, present storage to RAIDable SATA on the fly. That means plugging in the SATA drives in a Windows environment, just like USB, and allowing the intuitive software to take over. It's actually surprisingly easy in use and takes away some of the fear that a BIOS setup may arouse. So it's a case of either 2 x SATA + 4 x PATA devices or, if the PHY is taken up, 4 x SATA + 2 x PATA.


Sound and connectivity - The '8237's VIA Connectivity features support for 8 USB 2.0 ports but there's no provision for the other high-speed format we love, FireWire. VIA does offer the ubiquitous VT6307 2-port single-chip FireWire controller as an option, as well as the VT1622 TV-Out chip.

Gigabit LAN, via VIA's single-chip PCI-based Velocity Gigabit is an option that motherboard manufacturers may exercise. We'd like it if VIA could add in some on-chip support, or the kind of North Bridge-attached support that Intel currently provides as on extra. On an interesting sidenote, VIA offers a VPX2 companion chip for PCI-X support (2 x 133MHz). It still, however supports good ol' AGP 8x. With ECC support and PCI-X ability, VIA lays down foundations for a sever-orientated chipset.

Audio is becoming increasingly important on the very latest motherboards, so VIA offers manufacturers a couple of options. There's integrated 6-channel sound from the Six-TRAC CODEC that boasts 20-bit resolution, a 90dB Signal-to-noise ratio and a spiffy Stylus driver that incorporates Sensaura technology, or one could opt for the Vinyl Audio Gold onboard 7.1-channel surround sound solution powered by the impressive Envy24PT chip, which carries 8-channel support, 24-bit resolution and sampling rates as high as 96KHz. Yum. Of course, manufacturers are free to choose whichever sound subsystem they wish.

All in all, a pretty robust set of characteristics, from decent dual-channel implementation to the most impressive on-chip SATA support currently available to decent sound and connectivity options to PCI-X expansion. The proof, as they say, is in the pudding. Let's take a brief look at the reference board and then begin the benchmarking run.