Asus P4S800D-E Deluxe & Gigabyte 8S655TX Ultra: SiS 655TX Challenges Intel's Best

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