Reference board

If you recall our SiS 735 Performance Preview, the SiS 735 reference board was a microATX motherboard with one ACR slot, three PCI slots, and one AGP slot. While this may not sound like a lot, this is a pretty typical configuration for a reference motherboard.

SiS 645 system equipped with Ti 500 and 512MB DDR

A closer look at the system

With SiS 645, SiS wanted to showcase all that was possible with the SiS 645 chipset. Therefore, they went with a fully-fledged ATX motherboard with three DIMM sockets, six PCI slots, one AGP, and one ACR slot. In typical SiS fashion, buttons were provided for turning on the system and resetting it, making testing much simpler. An onboard speaker is also furnished on the reference board as are power LEDs for both the motherboard (red LED) and memory (green LED).

The sheer size of this motherboard is pretty incredible; pictures really don't do it justice. The SiS 645 reference board is definitely larger than your typical ATX motherboard. It's a good thing we don't run our systems in cases!

Like the SiS 735 chipset, the North Bridge of the SiS 645 reference motherboard shipped without a heatsink. Those of you familiar with AMD chipsets probably realize just how hot the North Bridge of the chipset can get. Many AMD-760 and KT266 motherboards not only ship with heatsinks, but also fans to keep the North Bridge cool. In the case of SiS 645, the North Bridge hardly needs a heatsink, much less a fan. Even under heavy load the North Bridge of the SiS 645 chipset barely got warm to the touch. We attribute this to the 0.18-micron manufacturing process it's designed around; most of today's chipsets are still built on 0.25-micron processes.

In terms of stability, the SiS 645 doesn't disappoint. We've been pounding at our SiS 645 reference board for days now without a single lockup in Windows XP Professional. In fact, the reliability of this board reminds us of the production Intel 850 motherboards we've been using for months without incident. We consider this to be a very impressive feat for a reference motherboard, only the SiS 735 chipset matches SiS 645 in terms of stability of a reference product. We have a very strong feeling that the SiS 645 chipset will be regarded as one of the most solid platforms for the Pentium 4 processor.

Bus adjustments

BIOS main menu

Memory compatibility Our SiS 645 reference motherboard performed flawlessly with all the DDR modules we threw at it. For DDR333 mode, a module from Kingmax was provided, but we were able to run our CAS2 DDR266 Micron modules at DDR333 with no problems. Off the shelf generic DDR266 modules we purchased (using Nanya chips) didn't work reliably in Windows XP in DDR333 mode, but ran fine when running at DDR266 (in spec).

We were also able to run our SiS 645 system with up to 784MB memory in DDR266 mode (via three DIMM modules) and 512MB of memory in DDR333 mode (via two DIMM modules). As we mentioned previously, the SiS 645 chipset only supports up to three DIMM modules in DDR266 mode and two modules in DDR333 mode.

Kingmaxx DDR 333