by January 1, 2000 0 comments

We regularly use loving names like BX, ZX, LX, etc, for motherboards. Have you ever wondered what these strange alphabets mean? These along with a sequence of numbers, define the chipset on the motherboard–the most important thing after the processor. The chipset is a set of chips that interconnect various parts of a motherboard. For example, the 440BX chipset forms a “host bridge” that binds the CPU with the main memory, the I/O subsystem, and the graphics card (through the AGP port).
Just like CPUs, chipsets also undergo constant development. For example, in the good old days of the Pentium, the 430TX was a popular chipset. Later, when the PII made its debut, the whole motherboard architecture changed, and so did the chipset. Initially, it was the 440LX. Later, as the PII raced up to higher speeds, and as more features were added to its architecture, the chipset also evolved to support them. After LX, the 440 series has seen many revisions–EX,
ZX, BX, and the BX-2. Now, Intel’s introduced a totally different chipset–the 810 series. 

The 810 chipset is radically different from the earlier 440 series. To start with, an AGP card is integrated in the chipset itself, so you don’t need a separate one. So, some of the 810 motherboards don’t have an extra AGP slot (This is a limitation if you want to use an AGP card of your choice). 

Another new feature is a new kind of digital serial bus known as AMR (Audio/Modem Riser). We’ll talk about this a little later.
The 810 has been divided into three parts. 

Graphics and Memory Controller Hub
(GMCH) 
This is a graphics engine capable of generating 3D graphics. The graphics are available at its output both in analog form for a standard monitor and in digital form, so that you can connect (through an encoder) to either a flat panel LCD display or your TV for playing games or watching movies. There’s a memory controller, which controls both system memory and display cache. The graphics engine uses Dynamic Video Memory
(DVM) that enables it to use system memory, instead of separate video memory. This means that the amount of shared memory will keep changing according to the graphics load. This prevents memory wastage compared to ordinary graphics cards, which have there own fixed memory that can’t be used for anything else. However, this could also be a limitation as the system will have to balance the memory load between the graphics function and the other resources.

The I/O Controller Hub (ICH)
The earlier 440 series chipset used an I/O controller known as X3 or X4. The PIIX4 (Also known as the I/O subsystem) acted as a PCI-to-ISA bridge, that is, it connected the ISA bus to the PCI bus which in turn was connected to the 440BX chipset. It also provided IDE and USB interfaces to connect hard disks, CD drives, and USB devices. The system BIOS and the keyboard were also connected to this chip.

The 810 uses what’s called the ICH, which has a different interface from the PIIX4. Known as the LPC (Low pin count, as it has only 7 pins) interface, this allows designers the choice of having an ISA bus or otherwise on their motherboards. You can give ISA support on an 810 motherboard by adding an ISA bridge chip. 

Another major difference in the ICH is the AMR slot. AMR is the result of a set of specifications known as the AC (Audio
Codec) ’97 specification. Usually, sound and modem cards have both analog and digital circuits. You have to be very careful while designing them, because digital circuits generate a lot of “switching noise” that’s easily picked up by the analog circuits, just as your TV and radio pick up noise when fluorescent light sources are switched on or off. In AMR, the digital part is integrated into the ICH and the analog circuitry resides separately on the AMR card, thus giving a better signal-to-noise ratio than
PCI/ISA sound and modem cards. So, since only half of a normal PCI/ISA sound/modem card resides on the AMR card, these are smaller and will be cheaper. It also explains why the AMR slot has fewer pins than a PCI slot.

Firmware Hub (FWH)
The firmware hub stores the BIOS code, so you can use this and eliminate the current external BIOS ROM. It also has a random number generator
(RNG), which can be used for security-related applications like e-commerce and digital signatures. The RNG uses white noise generated on the chip to generate numbers. We saw that digital circuits generate a lot of noise. What better way than this to put noise to good use? This also reduces the chances of repeating generated numbers, because it’s very difficult to repeat noise patterns. 

What next? 
The Intel 820, which will shortly follow the 810, incorporates support for a few additional features. It has support for
RDRAM, which provides twice the bandwidth of conventional PC100 SDRAM. And like the 810E the 820 will have a 133 MHz front side bus. The Intel 840 is targeted at high-performance multiprocessor systems, such as servers. Intel claims that its internal direct AGP port provides a bandwidth of 1gbps and dual RDRAM channels give it a peak transfer rate of 3.2
gbps. Both these chips will be based on the 810’s architecture.

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