Today there remain no doubts that very soon DDR SDRAM will become a basic memory type for modern PCs. The rivalry Rambus has finally lost its ground, and even Intel now offers Pentium 4 chipsets with DDR SDRAM support. As long as DDR SDRAM sports a lot more attractive price than RDRAM, the market share of the latter will shrink dramatically. However, the failed attack Rambus undertook to retain its positions is likely to seriously hit some manufacturers. At least Intel, an ancient fierce supporter of RDRAM, can no longer be regarded as a chipset manufacturer #1. For Intel the situation with Pentium 4 chipsets still looks favorable enough since for a long time Intel's policy was not to license any third parties to use a corresponding CPU bus. Nonetheless, Intel now faces some strong competitors in this field. This time we'd like to tell you about one of today's most successful DDR chipsets for Pentium 4 CPUs, SiS645.

Let's highlight the advantages of SiS645 as compared to the other DDR chipsets. Firstly, it supports the fast and relatively cheap DDR SDRAM, which makes it more promising than i850 with RDRAM or i845 with PC133. Furthermore, SiS645 is the only DDR chipset with DDR333 support. The bandwidth of this memory type is 25% greater than that of PC2100 DDR SDRAM used by all the other DDR chipsets. Besides, SiS645 boasts high performance when working with the common PC2100. In most tests it overruns i845D and is only a trifle slower than VIA P4X266A, which is still an illegal product, because VIA doesn't have Intel's license for Pentium 4 bus. Secondly, SiS645 is the cheapest Pentium 4 chipset, so SiS645 based mainboards offering a standard bunch of functions cost about $100.

Of course, most users stick to the opinion that only Intel can create really stable chipsets, and SiS645 will never catch up with i845D in this respect. Well, the tests show that this opinion is absolutely ungrounded and SiS645 based mainboards prove quite reliable. For example, the leading OEMs, like Compaq or Hewlett Packard, have already made up their mind to use SiS645 in their PCs. And hardly anyone will doubt that these companies pay due attention to quality matters.

  

We would like to remind you that some years ago chipsets from SiS were fairly treated as the best solutions for i486 PCs. SiS' subsequent withdrawal from the chipset market was caused by no sharp fall in the chipset quality, but it was for production troubles. For several years the tension between SiS and UMC prevented the chipset developer from getting access to the production capacities that is why SiS couldn't get back to the market. Today SiS has semiconductor production lines of its own and doesn't depend on the other chip manufacturers any longer.

Despite the protracted standstill SiS didn't lose its potential. For example, after the company's return to the market, SiS engineers managed to develop an impressively fast DDR memory controller, which turned out a real headache for VIA, SiS' main competitor. As a result, VIA even had to launch an improved version every time they announced a new chipset, so that they could compete with SiS solutions on equal terms. Moreover, SiS performs pretty well in the 3D chipset market as well.

For these reasons we were keen to take a closer look at SiS645 based mainboards. Another fact that warms our interest is that in the immediate future nearly every huge mainboard maker will launch a product of the sort. In this review we'll deal with three products based on SiS645 chipset, which were the first to enter the market. They are:

• ASUS P4S333
• ECS P4S5A
• MSI 645 Ultra

Mainboard Specifications

All the other components of these reference systems coincided with the list given above for SiS645 based systems.

We ran all the tests in MS Windows XP operation system.

Performance

First of all, we launched wcpuid utility to measure the clock frequency of the CPU on each mainboard. It's obvious that the performance of a component can heavily depend on the real CPU frequency on a certain mainboard. Some manufacturers take advantage of this phenomenon increasing the real FSB frequency in order to bring up the CPU frequency. The test we supply below will help us to unmask the cheaters:

As you can see, only ECS didn't resort to this trick. MSI and ASUS tried to increase the performance of their SiS645 based mainboards by about the same 0.7%-0.8% with the help of slight overclocking. So, as you look through the test results, please, bear in mind that ECS P4S5A is a more "honest" mainboard.

Now let us take a look at the benchmarks results. The first thing to test was the actual memory bus bandwidth measured in SiSoft Sandra 2001:

The results of this benchmark prove the theory. The only thing we could mention here is the slower memory subsystem of ECS P4S5A compared with that of the other two rivalry mainboards. Besides, the extremely low results shown by SiS645 with PC133 SDRAM compared with i845 also catch our eye at once. Well, we shouldn't expect anything more from SiS645 here. First of all, the memory controller of this chipset is optimized for DDR memory, so it positively cannot outrun the specific PC133 SDRAM controller of i845. As for the performance of SiS645 with DDR266, it's nearly the same as in case of i845D, a DDR chipset from Intel.

Now let us find out how the results of this synthetic test correspond to practice.

In this test the SiS645 based mainboards from ASUS and MSI are the best. Nevertheless, they fail to catch up with the i845D based mainboard in case of DDR266. When we installed DDR333 into the systems with MSI 645 Ultra and ASUS P4S333, they even got close to the i850 system with RDRAM, which bandwidth is circa 20% higher than that of DDR333.

In content creation applications we can witness the triumph of ASUS P4S333, which surprised us having beaten the i850 based mainboard in case of PC2700 memory. The regular PC2100 DDR SDRAM leveled out the results of i845D and the two SiS645 based boards from ASUS and MSI. We were upset to see ECS P4S5A lag behind in this test. Its results looked still more deplorable when we used PC133 SDRAM: this generated a 17% gap between P4S5A and i845 working with the same memory type.

In typical office applications the mainboards on Intel chipsets look much better than their SiS645 based competitors. No wonder: office applications are highly sensitive to the disk subsystem performance. Intel chipset based mainboards with ICH2 South Bridge use a specially developed caching ATA-driver aka Intel Application Accelerator. SiS on its part, doesn't have anything of the kind yet.

In gaming test the situation changes a bit. ASUS P4S333 with DDR333, which has always been one of the leading racers, moved down the list and is now in the same position as ECS P4S5A used to be. The new leader is MSI 645 Ultra breaking ahead of the i850 based mainboard. When we tested with DDR266, the old tradition returned: ECS P4S5A fell in the very end of the group again. Not to mention its performance with PC133 SDRAM.

Higher resolution and level of detail don't affect the results. In gaming applications SiS645 can act as a serious competitor to i845D and even to i850.

In Unreal Tournament ASUS P4S333 with DDR333 regains its leading position. Well, as soon as we replaced PC2700 DDR SDRAM with PC2100 DDR SDRAM, P4S5A fell behind MSI 645 Ultra.

In this game the results correspond to the factual memory bus bandwidths. MSI 645 Ultra is the fastest with both DDR333 and DDR266, the other two mainboards don't lag much behind though.

3DMark2001 appears an ideal test for MSI. Here it turns out smart enough to outpace the other competitors even with faster memory. At the same time, ASUS P4S333 shows the worst results in this test for some reason.

Overclocking

When choosing a mainboard, most users pay particular attention to its CPU overclocking functions. That's why we couldn't leave out overclocking in this review. But before we pass over to our achievements, let us remind you what overclocking functions the three SiS645 based mainboards boast:

Apart from the available overclocking functions, there are quite many other factors to influence the result. These can be the layout quality, component quality, or even chipset cooling. In this respect, we'd like to note that the North Bridges of all mainboards we tested this time are provided with heatsinks but do not have a cooler. On the MSI and ECS boards it is fastened with a sticky pad, and on ASUS P4S333 it is pressed with a clip to the chip surface covered with a layer of thermal paste.

We found out that the Vmem on MSI 645 Ultra was a bit lower than the nominal level. As a result, memory on this mainboard overclocks a bit worse than that on ASUS P4S333, for instance.

Now let us discuss the practical results. For our testing purposes we took Intel Pentium 4 CPU with an unlocked multiplier, then decreased it and tried to squeeze the highest possible FSB frequency from each mainboard. Since their stability was also influenced by the power supply unit, we took a high-quality 30W PSU from Jou Jye Electronics Co., LTD (Power Master), JJ-300-A, for this test.

Our tests showed that ASUS P4S33 had the best overclocking potential. The top FSB frequency we obtained on this board totaled 158MHz. MSI 645 Ultra was not much weaker. The maximal result for this mainboard was 151MHz. The third racer, ECS P4S5A got disqualified at the very beginning: this board doesn't allow increasing the FSB frequency at all.

Conclusion

We have successfully hit the main objective of this test session, i.e., we proved that real SiS645 based mainboards are quite viable solutions. The three Pentium 4 novelties from SiS made by the leading mainboard makers demonstrated ample competitiveness in spite of the fact that mainboards built on Intel's DDR chipset for Pentium processors are already in stock. The performance and stability of SiS645 are no worse than those of i845D. All these advantages together with considerably lower price of SiS645 based mainboards and DDR333 support (which is absent by i845D based products) make it clear that SiS645 has hit the bull's eye.

As far as the three mainboards we tested this time go, each of them has its own highs and lows. Here they are:

• ASUS P4S333. This mainboard offers the biggest bunch of functions. It is equipped with an integrated six-channelaudio controller and voice diagnostics system. Besides, P4S333 sports the widest range of CPU overclocking functions. However, there is one very serious drawback: the price of this product is excessively high. For instance, this ASUS' mainboard is about 40% more expensive than a corresponding solution from Elitegroup and about 25% more expensive than the board from MSI.
• ECS P4S5A. The main advantage of this mainboard is its price. This is a quite wholesome Pentium 4 product selling at an outrageously low price. For example, in some shops it is available for nothing more than $85! P4S5A also supports PC133 SDRAM, which makes it attractive for those buyers who wish to upgrade their old system. In the meantime, P4S5A lacks some CPU overclocking functions and is quite slow, actually.
• MSI 645 Ultra. From our point of view, this mainboard offers the best price-to-performance ratio. It showed the highest performance of all and provided a sufficient bunch of overclocking functions. Its price falls near $100.