SiS755 Reference Board: Athlon64 from SiS

Final Words

When SiS asked if AnandTech would like to take a look at the SiS755 Reference Board, we really didn't know what to expect with the new SiS Athlon64 chipset. While past SiS chipsets for Pentium 4 had been outstanding performers and past Athlon chipsets had been innovative, there are few current SiS chipsets that seem to have everything to make them top performers. After looking more closely at the features of the 755, there was a little more excitement. On paper, the SiS755 is the first Athlon64 chipset to combine the ability to fix the AGP/PCI frequency with a full implementation of the 800MHz HyperTransport bus. In addition, while using a traditional North/South bridge chipset, SiS uses a 1GHz Mutiol bus between the chips to minimize the North/South bus as a potential bottleneck. The features of the 964 Southbridge are also fully competitive with SATA RAID, ATA133 IDE, 8USB 2.0 ports, integrated 100db Signal-to-Noise 5.1 channel audio, and 10/100 Ethernet. The only things that we might wish for are 100/1000 Ethernet and Firewire, both of which can be added by board manufacturers. On paper, at least, SiS755 appeared to be the best of current Athlon64 chipsets.

Features are one thing, but there is more to high-performance computing that a feature check list. To our surprise, SiS755 also provided the best performance in AnandTech benchmarks of any Athlon64 chipset that we have tested. This applies across the benchmarks, and there does not appear to be a weak area in the performance of the SiS755 Reference Board. Memory Latency is the best we have seen, Content Creation and General Usage are competitive with the best we've seen on A64, gaming sets new highs for A64 performance, and SPECviewperf performance is the best we have seen on an Athlon64. The margin over other Athlon64 chipset boards we have tested is generally small, but it is consistent. SiS755 provides the best performance of any Athlon64 chipset that we have tested, and we are looking forward to evaluating production boards based on the SiS755.

Just before publishing our SiS755 review, SiS announced the new 755FX chipset. Unlike past SiS chipset naming, the 755FX is not designed to replace 755. 755 is a chipset for Athlon64 and Opteron, though we have yet to see plans for an Opteron board based on 755. 755FX is a chipset for the upcoming Socket 939 Athlon64FX, which will run Dual-Channel memory and can use standard unbuffered DDR memory that you probably already own. As the first announced Socket 939 chipset, we were also surprised to see SiS list a 1000MHz HyperTransport bus as one of the 755FX features. It certainly would appear, based on this announcement, that SiS is having no problem manufacturing high-speed low-noise HyperTransport, which only promises further improvement in the stability and overclocking capabilities of the 755 chipset in the future.

Overclocking tests with the SiS755 Reference Board were the only area that was mildly disappointing. The overclocks we achieved were pretty average, and we expected better from a board that provides AGP/PCI frequency lock. As stated in the review, conclusions about overclocking capabilities of a chipset should never be made with a Reference Board, so this area remains inconclusive until we can run benchmarks on production boards. SiS certainly does provide the features to allow the best overclocking yet seen on an Athlon64, but this needs to be confirmed with real hardware.

We recently saw a production mid-range SiS755 board at Comdex produced by ECS. That board is on the way to our labs, and we look forward to performance testing. We are also hoping to see SiS755 boards soon from manufacturers that are famous for overclocking capabilities like Abit, DFI, Asus, and Gigabyte.

To our surprise, the SiS755 Reference Board is the best-performing Athlon64 chipset that we have tested. AnandTech is therefore pleased to award the SiS755 our Gold Editor's Choice as the best Athlon64 chipset. With 800MHz HyperTransport, the option to fix the AGP/PCI frequency, the ability to run DDR400 at the fastest 2-2-2-6 timings, and a full range of memory timing adjustments, the SiS755 is the only Athlon64 chipset that is not missing one or more of these features. When combined with the 964 Southbridge providing SATA RAID, ATA133, and 8 USB 2.0 ports, it is easily the best Athlon64 chipset that we have seen. Until we see the upcoming nForce3-250 and the rumored update to VIA K8T800, the SiS755 is the best Athlon64 chipset that we have tested.