SIS 655FX Ref Board Review (1)
Bluetooth 30 Sept 2003

SIS 655FX Dual Channel DDR400 chipset

The SiS 655FX is the next generation chipset supports P4 800FSB processors. It supports Dual Channel DDR400 and with its coupled SiS 964 South bridge, it brings SATA connectivity to this new platform. According to SiS, SIS 655FX is the first chipset to support 3 DIMMs Dual Channel DDR400.

Users are often troubled when they plan to upgrade legacy DRAM modules to satisfy requirements of dual channel motherboard in the fastest most convenient and cost-effective way. More often than not, they reluctantly make a costly investment in two DRAM modules. In addition, when three DRAM modules are inserted by accident, the dual channel function is disabled. Such restrictions can be cumbersome to get around with a dual channel motherboard.

Unlike other motherboards, the SiS655FX features world-class flexible dual channel motherboard architecture. Standard motherboards only accommodate two or four DRAM modules with identical specifications. However, the unique SiS655FX dual channel motherboard is extraordinarily versatile in structure. Even when inserting DRAM modules of various specifications on the SiS655FX, users can enable the dual channel function.

What's more, when other mediocre dual channel motherboards have a third DRAM installed, the dual channel function cannot function. With the flexible architecture included in the SiS655FX motherboard, the installation of a third DRAM does not disable the dual channel function.

Consequently, whether identical memory modules or a mixture of modules of different specifications are installed, the SiS655FX always makes dual channel mode possible, delivering high transmission bandwidths of up to 6.4 GB/s. This provides users the flexibility to upgrade and frees them from rigid memory module specification requirements. The SiS655FX dual channel motherboard's flexibility is a major asset to users with a need for high performance and versatility.

You might be confused how it works. It is easier to illustrate with an example as follows :

If you put 64 and 128 into channel 0 and put 256 into channel 1, system will think the channel 0 as 192MB (64+128) and will separate channel 1 into 192+64. The two logical 192M will work in Dual mode and the single logical 64M will run in single mode.

Memory controller, supporting Pentium IV FSB up to 200 MHz. The SiS655FX, via the second-generation 1GB/s Multi-threaded I/O link, interconnects the SiS964 Media I/O that integrates one EHCI compliant USB 2.0 host controller, 3 OHCI compliant USB 1.1 host controllers, the SATA150 controller, the ATA-133 dual IDE controller, AC 97 V2.3 compliant audio controller, and the Ethernet MAC controller with standard MII interfaced.

The SiS655FX Host Interface features the AGTL & AGTL+ compliant bus driver technology with integrated on-die termination to support Intel Pentium 4 series processors with FSB up to 200MHz. The AGP interface supports external AGP slot with AGP 4x/8x capability and Fast Write Transactions. The SiS655FX incorporates the second-generation 1 GB/s MuTIOL interface to bridge the SiS964 Media I/O. SiS MuTIOL technology is developed into three layers, namely the MuTIOL transaction layer, MuTIOL link layer, and the MuTIOL physical layer.

The SiS655FX Dual Channel Memory Controller, being the best Pentium 4 chipset in the worldwide that delivers 6.4 GB/s bandwidth way adequate and satisfactory to the 200MHz Pentium IV FSB bandwidth demand of 6.4GB/s, absolutely brings out the best performance of each other, and still has a lot to spare for the multi-I/O masters, and AGP masters. Foremost, based on the SiS655FX with optimized ball-out, a Pentium IV system featuring the Dual Channel memory subsystem can be realized in a cost-effective 4-layer PCB.

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