SiS755 Reference Board: Athlon64 from SiS
by Wesley Fink on November 23, 2003 11:19 PM EST- Posted in
- CPUs
SiS755 Reference Board: BIOS and Overclocking
AGP/PCI Lock and 800 HyperTransport
One of the biggest complaints with the VIA K8T800 is the absence of a PCI/AGP frequency lock. With the PCI/AGP frequency forced to float, overclocking becomes limited by the AGP card or PCI peripherals instead of the processor. System stability while overclocking is also compromised with synchronous AGP/PCI. SiS has implemented PCI/AGP lock on their recent chipsets, and it is also used on the SiS755. In addition, SiS runs the HyperTransport at a full 800MHz, instead of the lower speeds used on the nForce3-150 chipset. This combination of features makes the 755 the best Athlon64 chipset currently available, at least on paper.BIOS
Manufacturers will determine the BIOS used in production boards, but the BIOS used with the Reference Board influences the decision, since it is already a working BIOS. SiS uses the familiar Award BIOS in the 755 Reference board.
HyperTransport options, AGP, and Memory Timings are available in Advanced Chipset features. HT is running at 800MHz at default.
SiS has provided “word” options for DDR timings on recent chipsets. This is an option some end-users like, but it is generally criticized by enthusiasts, who prefer actual settings. SiS provides both options in their Reference 755 BIOS. As you can see, you can choose 6 levels of memory timings: Normal, Fast, Fast+, Fast++, Ultra, and Ultra+.
Or you can select “Manual” from the timing settings and set your own timings from a very large selection of memory timing options. Low-end versions of SiS755 boards will likely offer only the “Word” timings, but with full settings, mid- to high-end SiS boards will likely offer a full range of memory timing adjustments.
FSB Overclocking Results
Reference Boards are not really designed for overclocking, and there are no voltage adjustments available that we would see on boards with this option. However, with PCI/AGP lock available, we were anxious to see if the SiS755 did indeed perform better.| Front Side Bus Overclocking Testbed Default Voltage |
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| Processor: | Athlon64 3200+ 2.0GHz |
| CPU Voltage: | 1.5V (default) |
| Cooling: | AMD Stock Athlon64 Heatsink/Fan |
| Power Supply: | Powmax 350W |
| Maximum OC: | 2150MHz (+8%) 215FSB |
The above overclocking setup at default voltage allowed us to reach a stable Frequency of 215 at 800 HyperTransport with AGP/PCI fixed at 33/66. We really expected higher overclocks with the available PCI/AGP lock, but the potential for outstanding overclocking is at least there with the SiS755 chipset. By lowering the HT to 600 and slowing memory timings, overclocks in the low 220 range were reached, but nothing higher. At this point, we really need to see working boards from major manufacturers that specialize in overclocking to determine better the true overclocking capabilities of the 755 chipset. In overclocking, the 755 Reference Board with PCI/AGP fixed exhibited “either/or” performance. Either it booted (and if it did, it was stable no matter what was thrown at the board), or it did not boot, and it required a BIOS reset.
Reference Boards are rarely a good indication of the true overclocking abilities of a chipset because they are designed to qualify and demonstrate a chipset at design parameters. The features are here for the best overclocking in Athlon64 chipsets, but that has not yet been seen on the SiS755. Production boards should provide better answers to the overclocking questions.
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Googer - Thursday, December 16, 2004 - link
Lets Bench IT!MoronBasher - Saturday, December 6, 2003 - link
I have a sis 746, and 735 and i can't wait for this chipset to come out!!!mason - Thursday, November 27, 2003 - link
Great review!Two things -
1. The SIS reference board is almost always the fastest performing board with that particular chipset. I think it's premature to label it a winner until you can find a decent performing production board.
2. SIS has been making great chipsets for the Athlon since the 735, only no one knew about them because they typically ran second to VIA in memory banddwidth, which was what all the major review sites cared about. The HDD performance and overclocking headroom on the 735 and 745 both outclassed the VIA boards (KT266, KT266A, KT333) of the day, but they were hard to find and few manufacturers made anything better than cut-rate boards.
The MSI 745 Ultra and the Leadtek 735 board were possibly the best of the early generation SIS athlon boards.
The current SIS748 chipset for the athlon 400FSB is actually very good, though again slightly slower than the KT600 is memory bandwidth.
I just wish major sites would review the few boards that do use these chipsets, so we could start seeing higher quality boards like the DFI 748.
destaccado - Thursday, November 27, 2003 - link
buy now.....asus k8v is an awesome board, in 2 months you might as well wait another two months, and another.....jeeptreker - Wednesday, November 26, 2003 - link
Purchase timing is my concern. I'm considering the AMD 64 3200+ & the Chaintech ZNF-150 w/ nForce3-150 chipset for Christmas. Am I on the edge of a change? If I wait a month or 2 will the AMD 64 3400+ and SIS755 or nForce3-250 chipsets be out? If these items won't be out for 6 mos. then I'll just be chasing technology.Buy now or wait? Any suggestions will be appreciated.
Gimpus - Tuesday, November 25, 2003 - link
When should we expect motherboards based on the SiS755 chipset to reach retail chanels?NFS4 - Tuesday, November 25, 2003 - link
I'll wait til I see the performance of shipping boards before I jump ship...reference boards tend to be "tweaked" in some case. I'm currently lovin' my VIA K8T800 based Asus K8V Deluxe.justly - Tuesday, November 25, 2003 - link
"To our surprise, SiS755 also provided the best performance in AnandTech benchmarks of any Athlon64 chipset that we have tested."Did this realy surprise Anandtech? it didn't surprise me.
For quite some time SiS southbridge chips have proven to be well designed, in fact whenever disk preformance was tested SiS has had some of the best scores. The main problem SiS has had in the past was with the performance of their memory controller. So it would only make sence that when the memory controller is no longer a concern, as it is with the Athlon 64, SiS would be able to show of its southbridge performance.
Other than your surprise about the performance I thought it was a good article. I hope Anandtech doesn't ignore future SiS (or ALi) AMD solutions like it has in the past with socket "A".
Pumpkinierre - Monday, November 24, 2003 - link
I noticed your description of the erratic booting/stability behavior when overclocking which is similar to overclocking problems described in the ipkonfig article-today's AT news post:http://www.ipkonfig.com/Articles/AMDCastrated/Page... .Is this due to data corruption in the HT link as a result of CPU speed being linked to the HT link speed?
HammerFan - Monday, November 24, 2003 - link
I think performance will be influenced most by how "streamlined" everything in the chipset is (i.e. IDE drivers at maximum performance, things such as LAN and RAID taken off of the PCI bus and put on the Southbridge).