Abit KX7-333/KX7-333R DDR Athlon Motherboard
Last updated: 10/3/2002

CHIPS.  Altogether, a modern PC motherboard and the components it integrates consists of many millions of transistors and other parts with a complexity at the individual circuit level that goes beyond total understanding by a single person.  In fact, many of the components, including the motherboard itself, are so complex, that computers are required to design them.  However, a basic understanding and a proper context for reviewing a motherboard can be established with an overview of the principle chips it employs.

At the heart of the motherboard are the "glue chips," principle of which is is known as the chipset.  The KX7-333 motherboard uses the VIA Apollo KT333 chipset.  It consists of two chips:  the 552-pin VT8366A DDR North Bridge and the 376-pin VT8233 South Bridge.  The VT8366A is adjacent to the lower-left corner of the CPU socket and has a small fan on top of it. In the picture above, it is the one with "KT333" on it.  The VT8233 is 1 1/4" below the PCI expansion bus socket with large large VIA on it and the green boarder around it.

Simply put, the North Bridge controls the system and interfaces the CPU to the system memory and AGP display adapter.  The AGP graphics bus connects to the AGP display adapter slot on the motherboard and operates at 4X or 66 MHz.  The memory bus can be set to 100, 133, or 166 MHz.  It uses DDR memory technology to send data at twice the actual bus clock frequency for an effective speed of 200/266/333 MHz. This is done by transferring data on both the leading and trailing edges of the clock pulse.  In other words, the data is "double-pumped."  The Front Side Bus (FSB), which connects the CPU to the Northbridge, can be set to 100 or 133 MHz.  It has an effective speed of 200/266 MHz.  It is quite obvious that this Northbridge and the current generation of Athlons are a bottleneck when transferring data to and from 333 MHz DDR memory.

Instead of hanging the South Bridge off the PCI bus with a theoretical maximum burst speed of 132 MBytes/sec., which must be shared with all PCI peripherals, as it is done with older chipsets, the Southbridge is connected to the Northbridge with VIA's V-Link pipe, This is a 66 MHz quad-pumped--raising and falling edges of the pulse and the two voltages levels representing the 0 and 1 logic levels--bus for a 266 MByes/sec. transfer rate between the North and South Bridge.  Not only is it faster, it frees the PCI bus to deal strictly with peripheral devices and motherboard resources.

The Southbridge supports four ATA/33/66/100/133 devices (hard disk, CD-ROM, and DVD drives) with two ATA/133 controllers, each of which can (theoretically)  burst up to 133 MBytes/sec.  The chip supports six PCI slots (and has  three USB hubs supporting  two USB ports each.  It has a Low Pin Count (LPC) interface to implement legacy I/O functions, such as a floppy disk drive controller, and serial and parallel ports, with a Super Input/Output (I/O) chip.  An Advanced Programmable Interrupt Controller (APIC), Advanced Configuration and Power Interface (ACPI), Advanced Power Management (APM), and 6-channel AC/97 2.2 sound support are built-into the chip.  The Southbridge also has an MC/97 software modem interface, but it is not used by this motherboard.

The Southbridge adds an integrated 3Com Ethernet MAC controller for 10/100 MHz Ethernet and HomePNA phoneline network support.  The motherboard does not implement this capability either.

The KX7-333 employs the 128-pin Winbond W83697HF super I/O chip. It connects to the Southbridge's LPC interface and is located behind PCI slot 5 (counting from the right).   It includes:

• The floppy disk controller

• Two serial ports (UARTs), one of which supports infrared.

• Printer port

• Game and MIDI ports.

• Hardware monitoring...

• 2 thermal inputs

• 2 fan speed inputs

• 6 voltages

The specification in .pdf format can be downloaded here.

The RAID version of the board (the KX7-333R) includes the Highpoint HPT372 RAID controller and two additional ATA/133 hard disk IDE interfaces.  This chip is hung off the PCI bus as shown in the block diagram.  The HPT37x series of RAID controllers are covered in more detail in our guide to the Highpoint HPT370 ATA/100 RAID Controller Chip.

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