SiS 648 Performance Preview July 22, 2002 Brandon Bell

Introduction

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From zero to hero

While Silicon Integrated Systems (SiS) may not be a household name just yet, no other chipset manufacturer has been on as an incredible roll as the Taiwanese chip manufacturer. Just over a year ago SiS was a tiny player in the desktop chipset market, competing heavily with Acer Laboratories for that coveted third spot between industry veterans Intel and VIA Technologies. Rather than focusing on the desktop, SiS’ primary hopes lied in its chipsets for the mobile market. With an expensive, delayed, 0.18-micron fabrication facility just coming online, many industry analysts wondered how SiS planned to grow its business, much less continue to exist at all.

Then SiS shocked the entire chipset world with its SiS 735 chip. We were the first publication to report on its impressive combination of performance and stability. Unlike traditional DDR platforms that existed for the Athlon at that time, SiS 735 featured an innovative, single-chip design. By going the single chip route, SiS 735 offered an incredible amount of flexibility to motherboard manufacturers and its 1.2GB/sec of bandwidth was nothing to laugh at.

In terms of performance, our tests found no other chipset for the Athlon platform that could touch SiS 735. With its leading performance and lower cost, we figured it would only take a matter of months for the tidal wave of SiS 735-based motherboards to flood the market. Patiently, we waited, May and June went by with no new developments. Then July came and went with no changes. We didn’t get our hands on a retail SiS 735 motherboard until August: the ECS K7S5A. Performance of the board was excellent, just what we experienced a few months earlier with our SiS 735 reference board, and its sub-$100 price point made it an incredible value. However, the K7S5A had little room to work with for overclocking, turning off many hardware enthusiasts. Ultimately while many motherboard manufacturers designed their own SiS 735 boards, none of them came to market. As a result, SiS 735 was successful in the sense that SiS got their name in the heats and mind of the public, but SiS 735 itself was hardly a sales success.

Fast forward to Fall 2001. SiS’ next product, SiS 645, was truly able to deliver. With VIA’s well publicized legal battle with Intel over the Pentium 4 bus scaring away most motherboard manufacturers, an opening was created for SiS to step in and take the value and mainstream PC segments. SiS 645 offered performance that was extremely competitive with Intel’s 850 chipset with RDRAM at a significantly lower cost. As a result, motherboard manufacturers were now eager to hop on with SiS and a plethora of SiS 645-based motherboards were introduced.

In March 2002 SiS introduced its follow-up to the SiS 645 chipset, SiS 645DX. Not only did SiS 645DX beat Intel’s 850E chipset to the punch with its 533MHz bus, its release also predated the release of Intel’s 533MHz Pentium 4 CPUs!

Now just a few months later, SiS is back again with SiS 648 and once again it boasts an impressive list of new features. Most compelling is its support for DDR400 memory, and just as eye catching is its AGP 8X interface. But there’s more to SiS 648 than just those two features.



SIDEBAR: The original SiS 645 chipset was announced on August 23rd 2001. Just under a year ago.

The North Bridge

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Compatibility

The SiS 648 chipset is composed of the SiS 648 North Bridge (which connects the chipset to the CPU, graphics card, and system memory) and the SiS 963 South Bridge (which supports system peripherals such as the keyboard and mouse, and contains the hard drive and USB controllers among other items). If a motherboard manufacturer desires, the SiS 963 chip can be substituted for the SiS 961 chip from the SiS 645 family.

The memory controller

The heart of SiS 648’s North Bridge lies in its memory controller. Like previous SiS memory controllers, SiS 648 supports both synchronous and asynchronous bus speed operation. This means that the memory bus and system front-side bus can operate at the same speed or independent of each other. In particular, eight multiplier options are available for the memory bus, which can make things intimidating for the inexperienced computer user. With two system bus options to chose from (100MHz or 133MHz if you want to remain in spec) and four different memory types (DDR200, DDR266, DDR333, and DDR400) this adds for up to eight different combinations, ensuring support for every flavor of Pentium 4 system available.

Say for instance you wish to run your memory bus at 333MHz but your system bus at 400MHz. Simply select the “3:5” option for the CPU/RAM Freq Ratio setting, reboot the system, and you’re good to go. As we said earlier, this can be a bit confusing for those who are new to system building, so hopefully motherboard manufacturers will do a good job of explaining all the options available with SiS 648 in their user manuals.

Looking at the basic specs of the memory controller, you’d assume SiS left things virtually unchanged. Memory support is still limited to 3GB (1GB per DIMM, which is the same figure as SiS 645 and SiS 645DX); in comparison Intel 845/845E is also limited to 3GB while VIA P4X333 supports up to 4GB of memory. In addition, only two memory modules are supported in DDR400 and DDR333 modes, while up to three modules of DDR266 are officially approved. If it weren’t for the addition of DDR400 memory, the basic specs would be the same.

Despite this, SiS has assured us that the SiS 648 memory controller has been slightly improved. During our briefing, we were told SiS’ engineers had witnessed a two to three percent performance improvement with the SiS 648 memory controller over SiS 645DX. With this in mind, we were eager to see if this held up in our testing. You’ll have to read our performance results to see if this held true.

The other significant addition to the SiS 648 North Bridge is its AGP 3.0 interface. This officially brings AGP 8X (and its 2.1GB/sec of bandwidth) to the Pentium 4 platform.




SIDEBAR: SiS moved to its dual chip implementation with the SiS 64x series to cut development costs.

SiS 963 chip

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The South Bridge

As we stated earlier, motherboard manufacturers have two South Bridge’s to choose from for SiS 648: SiS 963 or SiS 961. The SiS 961 chip is borrowed from the SiS 645/SiS 645DX chipsets, and as such will likely only be used on SiS 648 motherboards intended for the value market. When the SiS 648/SiS 961 combination is used, bandwidth between the North Bridge and South Bridge is 533MB/sec, the same figure available on SiS 645/SiS 645DX. If SiS 963 is implemented, bandwidth jumps to 1GB/sec between both chips. In order to support this, SiS had to add a few pins to SiS 963, so it isn’t pin-compatible with the SiS 961 South Bridge.

Bandwidth

In particular, the pathway between the North Bridge and South Bridge is 16-bits wide and operates at 533MHz when the SiS 963 chip is used. Like SiS 645, the link between both chips is bi-directional. This means that two independent pathways have been implemented. One connection can send data from the SiS 648 chip to SiS 963, while the second pathway can simultaneously send data to SiS 648 by way of the SiS 963 South Bridge. In comparison, both Intel’s 845E and VIA’s own P4X333 chipsets offer 266MB/sec between both chips (although VIA’s recently announced P4X400 chipset offers 533MB/sec of bandwidth).

Other Peripherals

One new feature SiS 963 adds is support for the new USB 2.0 protocol. Offering up to 480MB/sec of bandwidth, USB 2.0 offers 40 times more performance than USB 1.1. Of course, USB 2.0 is backwards compatible with USB 1.1 devices; no new cables or connectors are necessary. Up to six USB devices are supported by the South Bridge.

Besides the new USB controller, SiS 963 also has a new IEEE-1394a “Firewire” controller. This is welcome news to the A/V world, as many consumer electronics devices have already implemented Firewire connections. In particular data rates of 100/200/400MB/sec are supported. Besides connecting your digital camcorder, the Firewire support SiS 963 offers can also be used to connect PCs without additional hardware. The Firewire controller built in to SiS 963 supports up to three devices.

Like SiS 961, dual hard drive controllers are implemented in SiS 963, although ATA/133 hard drives are now officially supported by the chipset. The onboard audio (six-channel) and networking from SiS 961 are also rolled into SiS 963.




SIDEBAR: Native “IP over 1394” support is offered in Windows ME/XP.

Test impressions/launch details

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The SiS 648 reference motherboard

The board layout of the SiS 648 reference motherboard is slightly different than the SiS 645DX board. Minute component changes were made, although at a quick glance some enthusiasts would hardly notice the difference.

Unlike SiS 645DX, the SiS 648 reference board we received lacked a heatsink on the North Bridge of the chipset. Prior to SiS 645DX, all the SiS motherboards we’ve received also shipped without a heatsink on the North Bridge. This keeps costs down for motherboard manufacturers, although we’ve noticed many retail SiS Pentium 4 motherboards with heatsink/fan combo units. Under heavy load the SiS 648 chip would get hot to the touch at 533MHz, but not unbearable. While previous SiS North Bridges were cooler, we still don’t think motherboard manufacturers will be forced to implement active cooling solutions on their respective products.

Stability

Stability of the reference board was excellent. We didn’t encounter a single lockup or crash in Windows XP during our testing while we were running the system within spec. When we attempted to run three DDR333 modules on the SiS 648 system some applications would occasionally crash, kicking us back to the Windows desktop but not locking up the system. The chipset doesn’t officially support three DDR333 modules, so the fact that it would run many Windows applications with no problems was a pleasant surprise, but we wouldn’t recommend it for consumers in mission-critical applications.

Compatibility

We mixed and matched many DDR266 and DDR333 modules from a wide variety of manufacturers and didn’t encounter any problems with the SiS 648 reference board. We’re still unsure how well DDR400 memory will ultimately run on the SiS 648 platform, as the only module we have was supplied by SiS for our testing.

Availability

Since we just discussed memory modules, we’ll start there first. As we just stated, SiS supplied us with a DDR400 module manufactured by TwinMOS Technologies. TwinMOS is a relatively new memory manufacturer that is based in Taiwan and is primarily available in the Asian market. TwinMOS DDR400 modules are in full production now and should begin slowly trickling onto the market, although we’re unsure if that applies to those of us here in the US. Besides TwinMOS, KingMax, Mushkin, and Corsair Microsystems are also currently shipping DDR400 memory modules.

In terms of motherboard availability, we’ve been told that ASUS, ABIT, ECS, and Gigabyte will likely be among the first to market with SiS 648-based motherboards. In fact, ASUS’s board (the P4S8X) will ship with Serial ATA hard drive support. ASUS Taiwan predicts availability in the July/August timeframe, although ASUS USA was less willing to confirm that date.



SIDEBAR: Serial ATA offers transfer rates of up to 150MB/sec.

System Setup

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Intel Pentium 4 2.53GHz

ABIT TH7II-RAID (for 1066MHz RDRAM tests)
Intel D850EMV2
SiS 645DX reference motherboard
SiS 648 reference motherboard

256MB Corsair XMS DDR333 CAS2 SDRAM
256MB TwinMOS CAS2.5 DDR400 SDRAM
256MB PC800 RDRAM

NVIDIA GeForce4 Ti 4600 reference board
Driver version Detonator 28.32

30GB IBM Deskstar DTLA 307030 ATA/100 Hard Drive
AFREEY 12X DVD-ROM

Windows XP Professional

DirectX 8.1

Desktop Resolution: 1024x768x32

Benchmarks

3DMark 2001 Second Edition - 32-bit color, 32-bit textures
Quake 3 Retail - High Quality
Serious Sam: The Second Encounter - Normal (32-bit) The Elephant Atrium demo
Jedi Knight II
SiSoft Sandra memory test
SYSmark 2002


SIDEBAR: ABIT has also announced their SiS 648 motherboard – the SR7-8X.

3DMark 2001

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3DMark 2001 - DirectX 8

Notes

Despite giving up roughly a gigabyte of bandwidth to 1066MHz RDRAM, the DDR400-based SiS 648 testing system comes out on top in 3DMark 2001SE. The margin is ultra slim though, less than 1% at all resolutions. When equipped with DDR333 memory performance drops off three percentage points at 1024x768x32, but it still offers enough performance to outrun Intel’s 850E chipset when paired with PC800 RDRAM.

SiS’ claims of improved performance over SiS 645DX also hold true, although we found the margin was only around one percentage point in 3DMark 2001SE.




SIDEBAR: SiS is not only the first to market with an AGP 8X Pentium 4 motherboard they’re also first when it comes to video cards. Their AGP 8X Xabre cards were launched over a month ago.

3DMark2001 Framerates

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3DMark 2001 - Car Chase

3DMark 2001 - Dragothic

3DMark 2001 - Lobby

3DMark 2001 - Nature

SIDEBAR: Samsung, the world’s largest memory manufacturer, has already begun production on its DDR400 memory chips.

Serious Sam 2

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Serious Sam 2 - OpenGL

Notes

SiS 648 continues to outperform the 850E/PC1066-based Pentium 4 system when outfitted with DDR400 SDRAM with Serious Sam. At 800x600x32, we witnessed a 2% performance advantage for the SiS platform. As we saw in 3DMark 2001SE, even the DDR333 SiS systems are able to outperform the PC800 RDRAM 850E platform, although DDR333 only gives up 500MB/sec of bandwidth to RDRAM, and keep in mind DDR’s lower latency.

SIDEBAR: For now all of the DDR400 modules on the market are CAS2.5 modules.

Quake III

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Quake III - High Quality

Notes

In Quake 3 the final results remain the same, although the i850E Pentium 4 platform is able to gain slightly on SiS 648 with DDR400 memory. SiS 648 continues to offer about 1.5% more performance than its predecessor, SiS 645DX when the test conditions are the same, indicating that SiS has indeed implemented some improvements in SiS 648’s memory controller.


SIDEBAR: SiS is rumored to be working on its own RDRAM-based Pentium 4 chipset. Unfortunately, we can’t comment on those rumors.

Jedi Knight II

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Jedi Knight II

Notes

The SiS 648 platform lands a clean sweep in all our gaming tests, coming out ahead again in Jedi Knight II.




SIDEBAR: We can tell you that SiS has additional Pentium 4 chipsets they plan to release this year.

Office/Content Creation Performance

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SYSmark 2002

Notes

SYSmark 2002 tests give the edge to SiS 648, although the margin overall is only one percentage point. The margins on all of these systems are incredibly slim, in SYSmark 2002’s Internet Content Creation test DDR400 only yields a one percent performance advantage over DDR333. Quite simply, if you’re going to be sticking to a lot of desktop applications, you might as well save a few bucks and stick with DDR333 memory for now.




Memory bandwidth figures have DDR400 and PC1066 RDRAM neck and neck. With roughly one gigabyte of bandwidth separating them, we expected the margin between both memory types to be greater, but it turns out that isn’t the case. Just as surprising is SiS’ DDR333 performance; the changes made to the SiS 648 memory controller were just enough to allow it to overtake Intel’s 850E chipset when equipped with 800MHz RDRAM.



SIDEBAR: DDR-II modules should begin to see the light of day next year.

Conclusion

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It’s looking like SiS has another successful product on its hands with its SiS 648 chipset. Like all of SiS’ previous Pentium 4 chipsets, performance is excellent, as is reliability. There really isn’t much to say against the SiS 648 chipset. Sure the memory compatibility question with DDR400 is still up in the air (especially since one true standard doesn’t exist), but this isn’t a criticism that you can aim at SiS, memory manufacturers definitely share some of the blame. Now that the platform is out there the compatibility question should be answered pretty quickly. For its part SiS has been testing their SiS 648 chipset with a wide variety of memory modules.

In a similar sense, you could also criticize the lack of support for more than two DDR333 memory modules. But again, this isn’t a limitation that is unique to SiS, Intel’s own DDR chipset only supports two memory banks (although many motherboard manufacturers are shipping motherboards with three DIMMs) and end users have definitely had their fair share of problems with VIA-based DDR chipsets and multiple memory modules.

So what cons can we find that are unique to SiS and its SiS 648 chipset? As far as we can tell, the only criticism we have with the chipset is that it isn’t available right now. Our tests indicate that SiS 648 isn’t just an excellent performer; it’s the fastest platform available for the Pentium 4 right now. While DDR400 memory modules don’t provide quite as much bandwidth as 1066MHz RDRAM on paper, SiS’ implementation with the SiS 648 chipset offers largely all of the bandwidth of RDRAM in our tests with SiSoft Sandra. When you combine this with the inexpensive price we’re expecting most SiS 648 motherboards to go for (right around the $100 price point), the choice becomes a no-brainer.

Now we’re just hoping that motherboard manufacturers won’t use the inexpensive price of the SiS 648 chipset as an excuse to position their SiS 648-based products solely in the value segment. We’re hoping for fully loaded SiS 648 motherboards with six PCI slots, onboard IDE RAID, and plenty of overclocking options for the overclocking community. SiS has delivered a platform with cutting-edge performance at an incredibly low price point. Now it’s up to motherboard manufacturers to fulfill their end of the equation and bring equally powerful products to market without breaking consumers wallets.

SiS’ experience with the Pentium 4 platform and DDR memory really shows in the SiS 648 chipset. Even Intel’s own DDR platforms are ages behind in features and performance. SiS deserves a lot of credit for bringing such an impressive product to market so quickly. It’s no small wonder why SiS has seen so much success over the course of the past 12 months.

SIDEBAR: Are you as impressed as we are with the SiS 648 chipset or do you plan on holding out for something more? Speak with others in the comments!