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Intel
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820E Chipset
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20 Design Guide
1.4. Platform Initiatives
1.4.1. Direct Rambus RAM (RDRAM*)
The Direct Rambus RAM (RDRAM) initiative provides the memory bandwidth necessary to obtain
optimal performance from the Pentium III processor as well as a high-performance AGP graphics
controller. The MCH RDRAM interface supports 266 MHz, 300 MHz, 356 MHz, and 400 MHz
operation. The latter delivers 1.6 GB/s of theoretical memory bandwidth, which is twice the memory
bandwidth of 100 MHz SDRAM systems. Coupled with the greater bandwidth, the heavily pipelined
RDRAM protocol provides substantially more efficient data transfer. The RDRAM memory interface can
utilize more than 95% of the 1.6-GB/s theoretical maximum bandwidth.
In addition to the RDRAM’s performance features, the new memory architecture provides enhanced
power management capabilities. The powerdown mode of operation allows Intel 820E chipset-based
systems to provide cost-effective support of Suspend to RAM.
1.4.2. Streaming SIMD Extensions
The Pentium III processor provides 70 new streaming SIMD (single-instruction, multiple-data)
extensions. The Pentium III processor’s new extensions are floating-point SIMD extensions. Intel
®
MMX™ technology provides integer SIMD extensions. The Pentium III processor’s new extensions
complement the Intel MMX technology SIMD extensions and provide a performance boost to floating-
point-intensive 3D applications.
1.4.3. AGP 2.0.
In combination with Direct RDRAM memory technology, the AGP 2.0 interface allows graphics
controllers to access main memory at over 1 GB/s, which is twice the AGP bandwidth of previous AGP
platforms. AGP 2.0 provides the infrastructure necessary for photorealistic 3D. In conjunction with
Direct RDRAM and the Pentium III processor’s new streaming SIMD extensions, AGP 2.0 delivers the
next level of 3D graphics performance.
1.4.4. Hub Interface
As the I/O speed has increased, the demand placed on the PCI bus by the I/O bridge has become
significant. With the addition of AC’97 and ATA/100, coupled with the existing USB, I/O requirements
will begin to affect PCI bus performance. The Intel 820E chipset’s hub interface architecture ensures that
the I/O subsystemboth PCI and the integrated I/O features (IDE, AC’97, USB, etc.)will receive
adequate bandwidth. By placing the I/O bridge on the hub interface instead of the PCI, the hub
architecture ensures that both the I/O functions integrated into the ICH2 and the PCI peripherals will
obtain the bandwidth necessary for peak performance. In addition, the hub interface’s lower pin count
allows a smaller package for the MCH and ICH2.