A Closer Look at SiS 655TX

While AnandTech was impressed with the features and value of the earlier Gigabyte 655FX, the performance found was nothing to write home about. So what has SiS changed in the 655TX incarnation to improve performance?


The most significant performance improvement in the 655TX is the reduction in latency by removing half the command cycles from the communication between the CPU and memory. SiS claims that this brings memory performance to 865/875 levels, which would be significant indeed since the Intel memory controller is a very good performer for a chipset-based controller.



Other features of the 655TX are very close to the 655FX, but they are refined to be more competitive with current and upcoming Intel chipsets. The 655TX is also paired with the 964 South Bridge to offer SATA RAID and 8 USB 2.0 ports for a very contemporary feature set.

Full Prescott Compatibility

655TX also fully supports FMB (Flexible Motherboard) 2.0 and VRM (Voltage Regulator Module) 10.0 specifications. This means full compatibility with upcoming Prescott processors. Both the Asus and Gigabyte manuals list Socket 478 Prescott processors as fully supported on their 655TX motherboards. Since there has been so much confusion and misinformation on the web about the new specifications, the FMB and VRM tables should help in better understanding what is required and the features provided in the new standards.

 FMB 1, 1.5, 2.0
 CPU Code Support  FMB 1  FMB 1.5  FMB 2
Willamette VRM9.0 60A
Northwood VRD10 60A 70A
Prescott VRD10 78A 91A 119A VRD10.1

 VRM 10.0 VS VRM 9.0
   VRM 10.0  VRM 9.0  Benefit of VRM 10.0
VID 6 bit 5 bit More accurate voltage adjustment
0.0125V 0.025V
Voltage Range 0.8375 - 1.6 1.1 - 1.85 Lower voltage
  • Northwood and Prescott dual support
  • Supports higher frequency CPU
  • Dynamic VID Yes No Supports CPU that can change Voltage on the Fly

    SiS655TX Specifications

    Advanced HyperStreaming™ Engine
  • SiS HyperStreaming™ Technology allows streams of chipset data to flow over all paths efficiently, concurrently, smoothly and intelligently. The SiS655TX Advanced HyperStreaming™ Engine further enhances the transfer rate on the path from host block to memory controller block to achieve lower latency that can improve whole system performance.


  • Host Interface
  • Support Intel Pentium® 4 HT FSB 800 CPU
  • Support Intel Hyper-Threading Technology
  • Support 800/533/400MHz Front-Side Bus


  • High Performance Dual DDR Memory Controller
  • Delivering up to 6.4GB/s Bandwidth
  • Performance optimization auto-configurability with flexible granularity via supporting the Dual 128x1 bit mode in symmetric DIMM types deployment, and the Concurrent Dual 64x2 bit mode with flexible DIMM types support
  • Up to 4 DIMMs of DDR400/DDR333
  • Support Un-buffered DDR DIMM and up to 1GB per DIMM
  • Suspend-to-RAM(STR)


  • Support AGP 8X Interface
  • Support AGP 8X/4X Interface
  • Support Enhancements of AGP Rev.3.5 Register Format
  • Support Fast Write Transaction


  • MuTIOL® 1G Delivering 1GB/s Bandwidth
  • Proprietary Interconnect between SiS655FX and SiS964
  • Bi-Directional 16-bit Data Bus at 533MHz Operating Frequency


  • SiS964 MuTIOL® 1G Media I/O

    MuTIOL® 1G Delivering 1GB/s Bandwidth
  • Proprietary Interconnect between SiS655FX and SiS964
  • Bi-Directional 16-bit Data Bus at 533MHz Operating Frequency


  • USB 2.0/1.1 Host Controller
  • One EHCI USB 2.0 Controller and three OHCI USB 1.1 Controllers
  • Support Total 8 USB 2.0/1.1 Ports
  • Support USB 2.0 High-Speed Device @480 Mb/s Transfer Rates


  • Serial ATA Host Controller
  • Two independent ports and flexible channel allocation
  • Compliant with Serial ATA 1.0 Specification
  • Support Ultra DMA 150
  • Support RAID 0, RAID 1 and JBOD configuration


  • PCI 2.3 Specification Compliance
  • Support up to 6 PCI Masters


  • Fast Ethernet/Home Networking Controller with MII Interface
  • Support 10/100Mb Fast Ethernet or 1/10Mb HomePNA 2.0 with External PHY


  • Audio/Modem Controllers with AC'97 Interface
  • AC'97 v2.3 Compliant
  • Support 6 Channels of AC'97 Speakers Out and v.90 HSP Modem


  • Advanced Power Management
  • ACPI 2.0 and APM 1.2 Compliant


  • Dual IDE Channels with Parallel ATA 133/100
    LPC 1.1 Interface
    Integrated RTC
    Integrated Keyboard/PS2 Mouse Controller

    Index Basic Features: Asus P4S800D-E vs. Gigabyte 8S655TX Ultra
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    • FFS - Wednesday, December 10, 2003 - link

      Q? to Wesley does these mobos have control of CPU fan speed (again like MSI Neo2), so it run more slow with low CPU load (= more silent)?
      Another one is how it's compatible with Radeon 9700 Pro? F.e. My SIS648 even with latest SIS-AGP drivers have have a conflict with Hercules R9700Pro when Fast Write is turned on...
      Competition is G R E A T E thing,... but you know we also want stability :))) So far, as I know Intel chipsets before were far more stable and compatible with other hardware...
      The bottom line "as fast" does not always mean "as good"... :(( And since I also love competition let's hope that SIS655TX as good as 875P.
    • ripdude - Wednesday, December 10, 2003 - link

      A good article on a serie of good boards, I'm very happy you took the P4C800-E dlx in the test.

      I'm more then happy with the increased competition these boards bring, the P4C800-e dlx is still about 199 in euro land.
    • SmoiL - Wednesday, December 10, 2003 - link

      When is the Asus P4S800D-E coming out? Nada on pricewatch
    • Wesley Fink - Wednesday, December 10, 2003 - link

      Several of the cells in the Feature Table on page 3 were reversed and have now been corrected.

      Dual Channel (2x64 bit) is called 128 bit mode on the SiS. The BIOS has the option to run 128-bit (Dual-Channel) mode or to force Dual 64-bit.
    • FFS - Tuesday, December 9, 2003 - link

      Also, as I remember VIA VT6307 support 3 (not 2) 1394a FireWire ports (as on MSI Neo boards), so why Gigabyte would cut them to 2 ???
      And besides Wesley always trying to stress out color-coded panel connectors.
      For me it's more important that you can change RAM without taking off videocard and ASUS had such problems with some of their mobos (now it looks better... but talking about overclocking ... hmmmm.
      Even it's damn stable: heatsink on ASUS SiS 655TX is passive (already -) and too close to CPU (plus wrong orientation - same mistake as with original
      P4C800 Deluxe. So - NO oversized cooler for CPU on this board.
    • FFS - Tuesday, December 9, 2003 - link

      Realtek ALC658 codec AC '97 2.3
      6-Channel with UAJ Shoud go to Gigabyte and vice versa...
      Oh well.., I had my SIS648 for a while and .. so now I'd rather prefer to pay eXtra for board with Intel chipset :((
      Plus Gigabit LAN will work faster(=better) with CSA...
    • FFS - Tuesday, December 9, 2003 - link

      Hey guys... In the features table on-board audio codecs are mixed up :)
    • Shalmanese - Tuesday, December 9, 2003 - link

      Er, I don't think Sis supports 33Mhz Memory speeds... (pg 5) ;).

      What happened to the tech support turnaround time bit? That was always the favourite part of your reviews.
    • Tokelil - Tuesday, December 9, 2003 - link

      On page 3 it says its the Gigabyte MB that uses the Marvel Gigabit controller, while on page 4 it says its the asus board that uses the Marvel controller... My guess is it is Asus that uses it and its wrong on page 3.
    • FishTankX - Tuesday, December 9, 2003 - link

      What on earth is the difference?

      There is no commercially avaliable 128 bit DDRSDRAM. All DDRSDRAM is 64 bit.

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