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The situation in the chipset market is changing fast nowadays. New chipsets used to become available to mainboard makers a few times a year, but now I have to review them monthly. And not just one but several products are often to be reviewed. So what's happening to the market? Why are the manufacturers trying to smother the market in their new wares?

I guess there is a simple answer. Competition. Competition among both: chipset makers and processor manufacturers, the latter promoting further innovations for their platforms to get more customers. Added the several constantly improving alternative memory technologies available and the present transition to the use of advanced standards: AGP 8x, USB 2.0, IEEE 1394, ATA/133, SerialATA and so on, there're wide possibilities to produce chipsets supporting various sets of various innovations. Rivaling chipset makers are racing to implement new technologies and announce new products. All to be in the lead. As only lazy one doesn't make chipsets nowadays, no wonder so many alternative variants are available.

Is it good for us, the customers? Yes, in a way. Innovations are implemented faster than before, chipsets are higher-quality and cheaper. We can buy a modern mainboard at a modest price. Fortunately, most of us have forgotten that an up-to-date mainboard may cost above $200. But there's the reverse side of the medal. The manufacturers pump us up in a different way. No sooner you bring home a new mainboard when it turns out to be not so up-to-date at all. In a little while new products start to support newer technologies by means of which a higher-performing system can be assembled. So in order to catch up with new technologies, we have to replace the mainboard oftener than we used to.

So today we're going to review new chipsets supporting new memory type - DDR400. One might wonder where to go next? Well, there are ways. In a few months these chipsets won't be the newest and highest-performing. Dual-channel DDR SDRAM chipsets are going to replace them. So read this article and wonder at the performance level achieved, but bear in mind that DDR400 chipsets are a kind of kings for a day as well as all their recent predecessors, though.

Well, too many words. Let's turn to the heroes of our story. They are VIA P4X400 and SiS648: two new Pentium 4 chipsets supporting AGP 8x and DDR400 SDRAM from VIA and SiS respectively. By the way, there are no such chipsets for Athlon platforms yet and it means they're going to come out soon. Then we'll have to talk about the pros and cons of 400MHz DDR SDRAM once again.

VIA: Wow, It Works: VIA P4X400

So what's P4X400? Actually it's the known to us P4X333 we reviewed last month with added DDR400 memory support (see our Roundup: Pentium 4 Chipsets Supporting 533MHz Quad Pumped Bus). That's the official position of VIA. I have a different opinion. I think P4X400 is a shaped up version of P4X333. I do mean that P4X333 was a kind of underdeveloped. Why? I'll explain.

Here are the reasons:

  • First, when I received a VIA P4X333 based reference-board, it already allowed to set DDR SDRAM rate to 200MHz (400MHz DDR). There was the usual option in BIOS Setup. But the option didn't work - memory was functioning at 133MHz instead. This was the first underdevelopment in P4X333, implemented correctly in P4X400.
  • Second, although P4X333 was supposed to support AGP 8x, the support wasn't there. P4X333 based mainboards only featured AGP 4x mode. SiS Xabre, the only graphics card for today that supports AGP 8x, refused to work in P4X333 based mainboards in that mode. This is the underdevelopment number two.
  • Third, P4X333 declared the support of the new version of the V-Link 8x bus. The bus connects North and South Bridges, but the new VT8235 South Bridge intended for that bus wasn't used in P4X333 based mainboards. The real products based on P4X333 featured the old VT8233 instead, that uses 266MB/sec. bandwidth V-Link, not the theoretically possible 533MB/sec.
  • Then, it's getting most interesting. It seems VIA wants very much to forget the existence of P4X333 and P4X400 chipsets. P4X333 is removed from the product list on the company's web-site and P4X400 wasn't announced in a separate press-release. Moreover, the P4X400 web-page compares it to the "fossil" P4X266 and P4X266A, not to its immediate predecessor P4X333.
  • The same fate befell the blue prints of P4X333 based mainboards from VIA division VPSD, which were also taken off the company's web-site.
  • Finally, the North Bridge chip model number is the same in both P4X333 and P4X400 - it's VT8754. That's the heaviest argument to prove that P4X333 and P4X400 are actually one and the same thing.

That's rather funny. VIA's new products roll out at lightning speed, and now they disappear as fast. Well, let's leave VIA's policy alone, as there's a long list of complaints to this company deserving a single review. Let's concern ourselves with the technical moments. Here's the flow chart of the new VIA P4X400:

So, among the new features of VIA P4X400 that do work now we'd like to mention the following:

  • Intel Pentium 4 CPU with 400/533MHz system bus support;
  • AGP 2x/4x/8x support;
  • DDR200/266/333/400 SDRAM support;
  • V-Link 8x connect between North and South Bridges with high bandwidth of 533MB/sec;
  • Integrated 6-channel AC-97 audio;
  • Integrated MC-97 modem;
  • Integrated 10/100 Ethernet MAC controller;
  • ATA 33/66/100/133 support;
  • 6 USB 2.0 ports support (three hubs).

We received the first mainboard based on the new P4X400 chipset for our tests. The P4PB 400 mainboard was manufactured by VIA itself (by its VPSD division, to be precise).

This mainboard follows the P4PB design, as the layout P4X400 is compatible with all VIA chipsets for Pentium 4. The fact that both mainboards are based on the same PCB is confirmed, by the way, as number "400" in the name of the board is written on a sticker glued to printed letters "P4PB".

As seen in the snapshots, P4PB 400 is equipped with an AGP slot, five PCI slots, and a CNR slot. There are three DDR DIMM slots so the maximum RAM capacity is 3GB.

VIA tried to equip its P4PB 400 with a certain number of extra controllers. It's funny, all the controllers are from VIA itself. Maybe such position accounts for the absence of IDE RAID or Serial ATA controllers as VIA doesn't produce them yet.

Soldered to the PCB, the 6-channel AC97 VIA VT1616 audio codec supports S/PDIF optical and digital outputs. That's why VIA P4PB 400 is equipped with an additional bracket with S/PDIF ports. Network support is implemented by means of the VIA Rhine III VT6105M controller. It's the most advanced LAN chip from VIA featuring 10/100MB Ethernet, Wake-on-LAN, and remote PC control. It comes with software for remote system monitoring and administration. The integrated IEEE 1394 VIA VT6306 Fire II host-controller and USB 2.0 support built into the South Bridge provide easy connect with all modern high-speed peripherals.

The component layout in P4PB 400 is rather convenient. The only uncertainty is the location of the ATX power supply connector. As ATX connector is situated in the middle of the PCB, the plugged-in power cable comes close above the CPU cooler hindering proper processor cooling. By the way, P4PB 400 can work without the additional 12-volt power cable.

We'd also like to mention that VIA, as well as many other manufacturers, ships P4PB 400 with the VIA FliteDeck software package that includes four utilities:

  • MissionControl - monitors crucial parameters such as voltage and temperature values and supports remote control via network.

  • JetStream - the utility for overclocking from the OS. Manual and automatic modes are available.

  • FlashPort - the GUI utility for BIOS update.

  • SysProbe - shows information on the system, including both hardware and software.

Overclocking capabilities of P4PB 400 are implemented through BIOS Setup. The mainboard allows changing FSB rate ranging from 100 to 200MHz with 1MHz step as well as CPU Vcore, Vagp and Vdimm.

In the end we should also note that as VIA hasn't yet agreed with Intel on "legalizing" its Pentium 4 chipsets, P4X400 based mainboards are hard to find in the market. It applies to P4PB too.

SiS: We're Not Hurrying Anywhere and Are Always in Time. Closer Look at SiS648

SiS has been more successful in chipset business than VIA recently. Reasonable marketing policy and advanced engineering solutions of the company have contributed to it. As a result, SiS sales volume is growing and company's chipsets, especially for Pentium 4 platform, gain higher reputation and supplant products from other Taiwan manufacturers, VIA and ALi.

A good quality of SiS chipsets is the implementation of new technologies and the absence of "underdevelopments". For example, DDR400 memory support was already implemented, although unofficially, in SiS645DX and since then the company has had wide opportunities to optimize and perfect it so that the new product could openly feature it.

Nevertheless, the official specs of the today-reviewed SiS648 don't claim DDR400 support still. What's the matter? Is SiS still uncertain about the efficiency of its memory controller at 200MHz? No, the point is elsewhere.

Firstly, SiS doesn't want to announce DDR400 SDRAM support until the status of this memory type is defined. Users are also evidently tired of the endless DDR memory subsystem speeding-up. That's why SiS decided to grant a respite, indirectly sparing users memory subsystem and overall platform upgrade. Well, anyway, SiS648 does support DDR400 SDRAM and this fact should be taken into consideration in the review.

Compared to its predecessor, SiS645DX, the new SiS648 has a lot of improvements so the chipset can really be considered new, but not another revision of the basic SiS645. Look at the flow chart:

So what's new in SiS648:

  • AGP 3.0 specification support. It means AGP 8x support and backward compatibility with 3.3-volt graphics cards.
  • Improved MuTIOL bus connecting South and North Bridges. Its clock-rate was increased to 533MHz so its bandwidth is 1.06GB/sec now.
  • New SiS963 South Bridge capable of using the 1.06GB/sec MuTIOL.
  • USB 2.0 protocol support by both hubs built into the South Bridge and all six USB ports.
  • Integrated IEEE1394 controller supporting three IEEE1394a ports and 400MB/sec bandwidth.

We should also add to the listed above SiS648 characteristics the ones that were inherited from the predecessor:

  • The support of Intel Pentium 4 CPUs with 400/533MHz system bus
  • Official support of DDR200/266/333 SDRAM and unofficial support of DDR400 SDRAM
  • Integrated 6-channel AC-97 audio
  • Integrated MC-97 modem
  • Integrated 10/100 Ethernet MAC controller
  • ATA 33/66/100/133 support

As SiS648 is a two-chip solution, the addition of new features went "smoothly". I mean that IEEE1394 controller implementation in the chipset didn't make SiS engineers to remove LAN controller as had been done in Athlon chipset of the company, SiS745.

We explored the SiS648 functionality with the example of the reference-board. Although there are not many SiS648 based products available yet, this chipset is sure to become widely spread. SiS products are popular among mainboard makers, due to their good characteristics, high speed, and low cost.

Let's have a look at the reference-board:

The reference-board has a huge size and is equipped with five PCI slots, an ACR slot, an AGP slot as well as three DDR DIMM slots. The PCB features an integrated IEEE1394 controller, AC97 audio, and a network controller. So the SiS648 based mainboard has the same capabilities as VIA P4PB 400, but SiS engineers didn't have to make use of additional chips for that. This is an important argument in favour of low cost of SiS648 solutions.

There's no need to describe the reference-board in detail as you can't come across it in shops. But there's one important point. SiS paid much attention to the stability of memory subsystem working at high rates in its reference-board. For example, the DDR DIMM power supply regulator is pulse, not linear as in VIA P4PB 400. We'll see later on that SiS' conscientious attitude like that will turn out highly efficient.

Contemporary Pentium 4 Chipsets Specs

This table allows comparing the features of the contemporary chipsets:

 Intel 850EIntel 845EIntel 845GVIA P4X400SiS648
North Bridgei82850Ei82645Ei82645GVT8754SiS648
Processor bus400MHz/533MHz Quad Pumped Bus (4.3GB/sec / 3.2GB/sec)
Processor interfaceSocket478
Memory typeDual-channel PC800 RDRAMDDR266
Unofficially supported memory typeDual-channel PC1066 RDRAM-DDR333 SDRAM -DDR400 SDRAM
Max. memory bus bandwidth 3.2GB/sec
Max. memory size2GB
4 RIMM slots
2 DDR DIMM slots
2 DDR DIMM slots
4 DDR DIMM slots
3 DDR DIMM slots
ECC support+ + - +-
AGP 4x/8x +/- +/- +/- +/++/+
Integrated graphics core - - + --
Inter-Bridge bus Hub Link 1.0
Hub Link 1.5
Hub Link 1.5
V-Link 8x
South Bridge i82801BAi82801DBi82801DBVT8235SiS693
Max. number of PCI Master 5 6 6 56
ATA-100/ATA-133 support +/- +/- +/- +/++/+
AC'97 + + + ++
CNR/ACR/AMR support +/-/++/-/++/-/++/+/++/+/+
10/100Mbit LAN+ + + ++
USB ports 4 6 666
USB 2.0 ports - + + ++
IEEE1394 ports - - --3

It's easy to notice that the launch of SiS648 returned SiS the title of the manufacturer of the most advanced chipsets for Pentium 4 platform. SiS648 has the highest performing bus connecting the Bridges and supports IEEE1394. The other features are at least level with competitors.

DDR400: Does It Really Work?

Before considering the chipsets performance, let's dwell upon the implementation of the DDR400 memory support.

Well, the first thing is that there's no DDR400 SDRAM standard yet. JEDEC approved DDR333 specification not long ago and DDR400 is actually "half-official overclocking" of DDR333 from 166MHz to 200MHz. So DDR400 is the name invented by chipset and memory makers implying that DDR SDRAM marked this way is good for overclocking.

The prospects of DDR400 becoming the industry standard seem vague today. JEDEC claims ordinary DDR400 memory couldn't work stably at such high rate and the transition to the new DDR-II technology is required. DDR-II uses slightly different signal protocols and voltage.

Samsung, one of the leading memory chip makers and main ideologist of the DDR400 idea, opposes JEDEC. The manufacturer claims they have already started the production of DDR chips that can work stably at 200MHz (400MHz DDR). Moreover, Samsung intends to promote DDR400 even without JEDEC's positive resolution.

Here I would like to make a comment. Although DDR400 has a gigantic bandwidth of 3.2GB/sec, the real DDR400 modules may perform worse than one might wish. The point is that memory makers have to increase the latency in order to ensure DDR400 SDRAM is stable. So while typical DDR266 memory modules available today have CAS Latency of 2, and DDR333 modules - 2.5, DDR400 modules produced today mostly work with CAS Latency of 3. That's why systems with DDR400 memory are often slower than analogous systems based on DDR333 SDRAM, for example.

Let's see what possibilities for memory subsystem configuration are offered by the tested chipsets. VIA P4PB 400 just has a BIOS Setup option setting the memory speed.

The usual set of options for timings is also available. The only addition to what we usually see is the possibility of setting CAS Latency to 3. Anyway, the P4PB 400 mainboard disappointed me with its unstable operation with DDR400 memory. Moreover, with default settings P4PB 400 performed worse with DDR400 than with DDR333. And this situation is very hard to change for the better even during fine tuning. VIA comments on this as follows: "As DDR400 standard is not ratified, we increase the timings greatly to ensure stable work and it inevitably leads to lower performance". Well, quite reasonable, I should say.

Let's see how things stand by SiS:

The number of memory settings offered by SiS648 based mainboard is beyond one's comprehension. SiS648 turns out to have so many memory frequency divisors that if SiS were not so modest it could announce not only DDR400 support, but something much more advanced. Just look what memory frequencies a SiS648 based mainboard allows setting:

Divider (FSB : Mem) FSB=100MHz FSB=133MHz
1 : 1 100MHz (DDR200) 133MHz (DDR266)
1 : 2 200MHz (DDR400) 266MHz (DDR532)
2 : 3 150MHz (DDR300) 200MHz (DDR400)
2 : 5 250MHz (DDR500) 333MHz (DDR667)
3 : 4 133MHz (DDR266) 177MHz (DDR354)
3 : 5 166MHz (DDR333) 222MHz (DDR444)
4 : 5 125MHz (DDR250) 166MHz (DDR333)
5 : 6 120MHz (DDR240) 160MHz (DDR320)
1 : 3 300MHz (DDR600) 400MHz (DDR800)
2 : 1 50MHz 66MHz
3 : 2 66MHz 89MHz
5 : 2 40MHz 53MHz
4 : 3 75MHz 100MHz (DDR200)
5 : 3 60MHz 80MHz
5 : 4 80MHz 106MHz (DDR212)
6 : 5 83MHz 111MHz (DDR222)

Impressive possibilities for setting memory frequencies definitely told on the quantity and quality of memory settings. The SiS648 based mainboard allows setting CAS Latency at 3 as well as changing all the other parameters within broader ranges than usual.

So much attention SiS engineers paid to the memory subsystem in their SiS648 also told upon the stability of work. The SiS648 based mainboard was functioning with DDR400 memory without any problems whatsoever.

Testbed and Methods

In this test session I compared all the up-to-date chipsets for Pentium 4 with 533MHz Quad Pumped Bus. In order not to overload the review with the results, the chipsets that work with DDR266 were omitted. Although such solutions are still widely spread (thanks to Intel's sluggishness), it makes no sense to use them today especially as DDR266 and DDR333 modules cost about the same.

Anyway, if you want to know about Pentium 4 chipsets performance with DDR266 memory - refer to our article called "Roundup: Pentium 4 chipsets with 533MHz bus".

Testbeds were configured as follows:

  i850E i845G VIA P4X400 SiS648
CPU Intel Pentium 4 2.4B (533MHz Quad Pumped Bus)
Mainboard Intel D850EMV Gigabyte GA-8IGX VIA P4PB 400 SiS 648 reference board
Memory 512MB PC1066 RDRAM - 512MB DDR400 CL2 SDRAM
Graphics Card VisionTek Xtasy GeForce4 Ti4400

All tests were run in MS Windows XP Professional, the mainboards were set to maximum performance (we used minimal timings).


First, let's see what synthetic benchmarks have to say about memory subsystem:

The bandwidth does grow as the memory frequency is raised to 400MHz. That's not a surprise. The other thing is funny: while in theory DDR400 SDRAM bandwidth is 3.2GB/sec, the same as by PC800 RDRAM, DDR400 systems do better in practice. It means that on the whole DDR memory works more effectively than dual-channel RDRAM. So the upcoming dual-channel solutions based on DDR SDRAM look very promising. But let's not rush ahead too much.

We should also mention that SiS648 is a little ahead of VIA P4X400 in this test (in case the memory frequency is the same). A month ago the situation was reverse, but SiS engineers seem to have enhanced once more the memory controller of SiS648, which had been used before in SiS645DX. Well, at least they optimized it for 533MHz Quad Pumped Bus as SiS645DX was intended for 400MHz bus only. VIA treated P4X400 simpler (see above) so its results practically don't differ from those shown by VIA P4X333 a month ago (I mean the results of operation with DDR333 memory).

The latency measurements show that VIA P4X400 with DDR400 SDRAM will not please us with good results. Memory subsystem latency is greatly increased in this case and it means that VIA didn't care about optimizing its controller for DDR400. That is, by the way, one more argument proving that VIA P4X333 and P4X400 are one and the same thing.

SYSmark 2002, which measures the platform speed in typical applications (Internet Content Generation: Adobe Photoshop 6.01, Adobe Premiere 6.0, Microsoft Windows Media Encoder 7.1, Macromedia Dreamweaver 4, and Macromedia Flash 5; Office Productivity: Microsoft Word 2002, Microsoft Excel 2002, Microsoft PowerPoint 2002, Microsoft Outlook 2002, Microsoft Access 2002, Netscape Communicator 6.0, Dragon NaturallySpeaking Preferred v.5, WinZip 8.0, and McAfee VirusScan 5.13), gave predictable results. SiS648 with DDR400 shows good performance, but the absolute leader is i850E, which works with dual-channel PC1066 RDRAM memory. VIA P4X400 with DDR400 suffered a tangible failure. Meanwhile if we use DDR333 SDRAM with P4X400 the results may be quite acceptable, almost the same as by other chipsets working with that memory. All this makes one think that DDR400 support in the VIA chipset is "optional" and the engineers didn't pay enough attention to the optimization of the chipset for this working mode.

SiS648 is again ahead of VIA P4X400. But they are both lagging behind i850E with PC1066 RDRAM…

When encoding video into MPEG-4 format, VIA P4X400 managed to fall behind all its rivals, even those, which worked with slower memory. The only conclusion is that the VIA chipset may hardly be considered able to work with DDR400. Actually the support of this memory type is nothing but a marketing trick.

In Quake3 Arena the results of P4X400 with DDR400 SDRAM disappoint even more. Meanwhile this chipset is quite good working with DDR333 memory.

Here's a rare example of DDR400 from VIA working faster than DDR333. Anyway, the previous results have proven that one shouldn't use DDR400 with P4X400.

One can only be pleased with SiS648 results. This chipset can gain wide popularity both for its capabilities and good performance.

SPECviewperf 7.0 is an excellent benchmark revealing the overall system performance and the memory subsystem performance. SPECviewperf results show that SiS648 with DDR400 memory and i850E with PC1066 RDRAM are especially strong in professional OpenGL applications. They are at the top practically in all the tests. But there are exceptions. In 3dmax-01 (based on 3ds max 3.1, in which three models are animated in OpenGL mode) DDR333 systems are pushing i850E with PC1066 RDRAM to the back, and in ugs-01 (based on Unigraphics V17) VIA P4X400 is quite unexpectedly in the first place.


One more test session makes one think once again that SiS and VIA have a certain "agreement". VIA handed Pentium 4 chipsets market over to SiS and SiS "promised" not to make any noticeable advances in Socket A chipsets market. Well, of course it's a joke, but it contains a scruple of truth.

The SiS Company is constantly releasing more and more successful chipsets for Socket478 systems. Their characteristics and performance level are improving, SiS chipsets for Pentium 4 are becoming more popular. At the same time SiS does quite poorly in Socket A chipset market. Socket A products from SiS are not widely spread and their features often leave much to be desired.

VIA, in its turn, doesn't try hard enough to make good Pentium 4 chipsets or even get the license from Intel for the processor bus. Meanwhile, Socket A chipsets from VIA are selling as hot cakes. And this is quite natural. The features and speed of KT chipset family from VIA remain among the best for quite a long time already.

Two new products reviewed here, VIA P4X400 and SiS648 chipsets, are nicely fitting into the scheme. SiS has produced a next potential hit featuring best characteristics and excellent performance for today. VIA announced a somewhat strange chipset featuring nothing special.

As for DDR400 memory, its use with SiS648 (not with VIA P4X400, which works not very fast with DDR400 SDRAM) allows to reach a new performance level. The speed of this solution is higher than in platforms using dual-channel PC800 RDRAM. Moreover, SiS648 with DDR400 SDRAM can often compete with PC1066 RDRAM systems. 

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