The release of the single-channel i848P chipset with its unexpectedly outstanding characteristics, which had put Intel's Spring chipsets into an awkward position (they had two channels!) was a real success. In contrast to the past-oriented i865P with vague prospects, this chipset uses all features of Intel's modern south bridges and has no crippled north bridge components. One memory channel is locked but if 2GB RAM is enough for you, the only i848P disadvantage will be its speed.
What about the competitors? They have no dual-channel solutions for new processors (with 800MHz bus) to offer (the SiS655FX/TX and VIA PT880 chipsets are ready, but we still haven't seen any boards on them). At the same time, cheaper single-channel chipsets (the price was always an advantage of VIA and SiS) have been announced quite a long time ago, and today we are going to test the first SiS648FX and VIA PT800 solutions. But first, there's information on chipsets architectures.
Its predecessor got some very high score in its time: at that moment it was the strongest competitor for i850E+RDRAM(PC1066) tandem, and SiS648-based boards with DDR400 support were cheaper than the top Intel+Rambus combination. Unfortunately, it had no Hyper-Threading support: the release of revision B had been postponed, and without such support the chipset wasn't of much interest among top solutions. Then the company released the dual-channel SiS655 (putting aside the SiS R658), which however hadn't set any new records. And after the announcement of Intel's new Pentium 4 line with 800 MHz FSB alongside a dual-channel chipset series, SiS had been keeping silence.
Today we're going to test the first serial mainboard on SiS648FX we got. The product hasn't obtained any considerable new features, so the company just added "FX" to the name. What's changed in SiS648FX comparing to SiS648? Have a look at its block diagram.
The picture from the SiS website is out of synch with reality :). First of all, SiS648FX officially supports DDR400 (in contrast to its predecessor). Second, 800MHz FSB support is not shown in the diagram at all. There are no more differences between the chipsets. The chipset is officially coupled with SiS963L south bridge, while SiS648 is coupled with its complete version - SiS963 (that is more expensive due to integrated FireWire). This situation perfectly illustrates the changes: while SiS648 has been developed to be a performance and functionality leader, SiS648FX is aimed at the low-end sector. Remember that all the latest south bridges from SiS are pin-compatible and have the same interface to north bridge, so mainboard manufacturers can easily replace them (if they want).
Here are chipset brief specs (the south bridge features are given for the recommended SiS963L):
There's neither Serial ATA, nor FireWire. However, there's one more interesting feature we'd like to attract your attention to - HyperStreaming. This is SiS' proprietary technology integrated in all its latest chipsets. It's obvious that SiS began promoting its products using beautiful logos and esoteric terms. The matter is that all components of the HyperStreaming technology have been supported in SIS chipsets for over two years already and only now they are united under a single name.
The idea of this technology is that the north bridge memory controller can operate in several modes.
Well, there's nothing revolutionary actually, let's see what the real scores will be.
This chipset is the standard extension of VIA's Pentium 4 line. The line was renamed from P4X to PT for unification purposes (with KT series for Athlon XP) and got the "800" postfix (though it's meaning is not clear). Its P4X400 predecessor is reviewed here (note that boards on the new stepping of the chipset do support DDR400 memory, though it doesn't accelerate them in any way).
Here are chipset brief specs (VT8237 south bridge):
Compared to P4X400, it supports Intel's new processors, has better memory features (max. capacity, ECC support), uses a new south bridge with more USB2.0 ports and supports Serial ATA. If we compare VIA PT800 to its direct competitors (single-channel Pentium 4 chipsets), this will be the most functionally advanced chipset. So what about the performance?
OS and drivers:
First come the low-level memory controller tests, especially interesting due to Hyper-Threadi... oh sorry, HyperStreaming in the SiS chipset.
The latency is not low at all in the SiS648FX (well, SiS doesn't really compare 648FX with i848P and PT800 in its documentation). Judging by the data obtained, Intel's chipset might take the lead (with traditionally high write speed) and VIA's new solution might take the middle position. Now let's run our favorite benchmarks to reveal the real difference in the way memory controllers work.
The best benchmark is the one that compresses a large data volume with some archiver utilizing a complicated algorithm and a large dictionary that uses tens and even hundreds of memory megabytes. SiS falls behind by 16%, while PT800 yields less than 3% to the leader.
In case of MPEG4 encoding we don't have such difference: SiS648FX has caught up with VIA and even outscored it (i848P beats both by 3%).
Remember that not all applications depend on memory speed. For example, MP3 encoding depends exclusively on CPU clock.
One of the best external rendering modules for 3ds max (Brazil Rendering System) slows down SiS648FX a little (about 3%) comparing to its competitors.
The Photoshop scores look curious: VIA outscores SiS by 3%, but Intel 848P unexpectedly falls into the last place losing 1.5% to SiS648FX. We don't see any reasons for that. However, that was the only artifact during the tests.
You can see that all the game scores look identical. SiS remains an outsider, VIA PT800 outdoes it by 5-7%, and i848P by 6-10%.
All three single-channel chipsets for modern Pentium 4 processors (we don't consider ALi products) have very close north bridge characteristics. There's nothing to improve until they move to PCI Express, and the only difference is memory type and maximum capacity supported (but not the clock speed). VIA PT800 looks the best with its ECC support, which is a rare thing for budget chipsets (on the other hand, i848P has the CSA bus). South bridges might differ on different mainboards, but we'd like to distinguish VIA VT8237: ICH5 doesn't support Serial ATA RAID (though there's also ICH5R version), and SiS963L doesn't support Serial ATA at all (plus the FireWire lack).
The i848P is the fastest runner in this pack, though VIA PT800 yields only
3%. But remember that Intel's chipset was represented by the fastest
board we tested, while for VIA chipset we only touched one model so far.
SiS648FX loses 3 to 10 % (sometimes even more). Again, there's
only one board based on this chipset in our testlab, but the gap is too great to be
ignored. Taking into account the scarce functionality and low performance
of SiS648FX among all three chipsets, its price is the most powerful feature.
However, SiS has the newer dual-channel SiS655FX (which adds the 800 MHz
FSB to a quite good SiS655) and its successor SiS655TX
(which supports Advanced HyperStreaming). Well, the company does
have dual-channel solutions to offer, and you might remember that
Intel's dual-channel chipsets without PAT are quite close to i848P by performance,
so don't take all that marketing rubbish about number of memory channels to your heart.
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