SiS 771 Reference Board Review

SiS 771 is a chipset with integrated graphics targeted to the AMD platform to be released by the end of this year. We’ve got from SiS a reference board for this chipset and since motherboards based on the same chipset usually achieve similar performance, you can have a clue on what performance to expect from motherboards based on the forthcoming SiS 771.

A reference board is a motherboard manufactured by the chipset maker to make internal tests and also to ship to their partners (i.e. motherboard manufacturers) so they can create their own products based on the given chipset.

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Figure 1: SiS 771 reference board.

As mentioned, SiS 771 has integrated graphics (“on-board video”), based on the new Mirage 3 graphics engine, which is a truly DirectX 9.0 (Shader 2.0) engine. Compared to other chipset makers, SiS is quite outdated. Only now they are coming with a DirectX 9.0 (Shader 2.0) part, while other manufacturers have DirectX 9.0 engines for years now, with some of them – like nVidia – with DirectX 9.0c (Shader 3.0) parts for quite a while. It is also important to keep in mind that DirectX 10 is right on the corner, with nVidia promising to launch products based on this new programming model next month.

On the other hand, SiS chipsets are traditionally one of the cheapest around, meaning that in the near future the cheapest socket AM2-based computers around the world will be based on SiS 771 for sure, thus the importance of this review.

Of course gamers won’t even think of buying computers with on-board graphics, so why place a 3D accelerator on the motherboard? Budget Joe may want to buy the cheapest computer around and at the same time try to run light games. Of course if one wants to run high-end games, on-board graphics and cheap computers aren’t the right choice.

Thinking of the increasing interest in playback video quality, SiS added some 2D enhancements to SiS 771, which makes perfect sense for the average Joe, who wants to watch some videos and may even consider using a SiS 771-based motherboard as the core of his/her multimedia center PC. These enhancements include a slice layer accelerator, a video scaler, a deinterlacer and a motion compensation engine. This means that the chipset is used for those functions when you play a MPEG2 file or a DVD, instead of using the CPU, improving the system performance and image quality.

SiS 771 also supports a high definition video link to support DVI outputs, however motherboard manufacturers wanting to implement this feature will need to add a SiS 307 chip on the board.

Even though SiS 771 has integrated graphics, it supports one PCI Express x16 slot. Keep in mind that motherboard manufacturers in order to cut costs may offer SiS 771-based motherboards without this slot, but this limitation is of these particular motherboard models.

As AMD64 CPUs have their memory controller embedded, the north bridge chip doesn’t play any role on memory access performance nor on the capacity and limitations of the memory types and sizes the system can have. The motherboard manufacturer can, however, implement less memory sockets than usual (i.e. less than four sockets).

The south bridge chip defines other features that will be found on SiS 771-based motherboards. The reference board we got used a SiS 966 south bridge, but motherboard manufacturers can choose to use a different south bridge chip, like the forthcoming SiS 968.

SiS 966 main features are:

Two ATA-133 ports;
Four SATA-150 ports, supporting RAID 0, 1, 0+1 and JBOD;
Eight USB 2.0 ports;
Two PCI Express x1 slots;
Gigabit Ethernet;
High Definition Audio (eight channels, up to 192 KHz, 32 bits).

Keep in mind that the motherboard manufacturer may choose not to use all features provided by the south bridge chip.

Also, for the LAN port, the manufacturer needs to add a chip on the motherboard to make the interface with the physical layer. On SiS reference board this chip was SiS 196. To cut costs the motherboard manufacturer may use a Fast Ethernet (100 Mbps) chip.

As for the integrated audio, it is very important to keep in mind that the final specs will depend on the codec used, which is a small chip located on the motherboard. On the reference board SiS used a Realtek ALC883, which has a 95 dB signal-to-noise ratio (SNR) for its output and an 85 dB signal-to-noise ratio for its input, with 24-bit resolution. These specs are fair enough for the average user, but motherboard manufacturers may choose cheaper codecs in order to cut costs.

In summary, the final features of the motherboard depend a lot on the components the motherboard manufacturer chooses.

SiS 968 south bridge will keep the same basic specs as SiS 966, but with two SATA-300 ports and only one ATA-133 port.

For more information on SiS 771, visit http://www.sis.com/products/sis771.htm.

Let’s now take a look on its performance. On all benchmarks we configured SiS 771 video memory size as 128 MB, i.e. the system was “stealing” up to 128 MB of the main system RAM to use it as video memory. If you use a lower value the performance results will be lower.