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ECHNOLOGY

RIEF

(cont.)

ECG066/1198

AGPset Architecture

The 440LX AGPset (LX chipset) from Intel is designed primarily for the commercial desktop and
consumer desktop markets. However, some workstation vendors are deploying the LX chipset in
machines targeted for workstation applications. Key features of the LX architecture include

•

Single PCI bus

•

Single memory bus

•

66-MHz SDRAM memory

•

Advanced graphics port (AGP) bus for graphics cards

•

Support for up to two Intel Pentium II processors

Figure 9 illustrates the LX chipset architecture. The microprocessor, memory, and AGP graphics
buses operate with a peak bandwidth of 533 MB/s, while the peak bandwidth of the PCI bus is
133 MB/s. This contrasts with the 1.07-GB/s peak memory bandwidth and the 267-MB/s PCI
bus bandwidth of the Highly Parallel System Architecture.

CPU

Memory

Controller

SCSI

Controller

Di
sk

PCI Slots and
other Devices

PCI

Controller

AGP

Controller

Graphics

Controller

A single PCI bus provides
133 MB/s bandwidth for
all attached I/O devices

A single memory
controller provides
maximum bandwidth of
533 MB/s.

The AGP bus provides a dedicated path
for the graphics controller to
communicate with main memory and
processors. The AGP-to-memory bus
provides bandwidth of 533 MB/s.

Figure 9. Block diagram of the LX architecture.

The Highly Parallel System Architecture supports industry-standard EDO memory arranged in
2:1 interleaved banks. The LX architecture uses 66-MHz SDRAM technology, which Compaq
projects to be a very short-lived technology, based on imminent microprocessor and system
architecture advancements. Specifically, Compaq expects that 100-MHz SDRAM will be
available as soon as 100-MHz host-bus systems are available—sometime in the first half of 1998.
Since dual-processor LX workstations are not expected to be generally available until sometime
during the fourth quarter 1997, the 66-MHz SDRAM for workstations may have a useful life of
only about four to six months. Large purchases of 66-MHz SDRAM could result in large
obsolescence costs as early as next year, when users migrate to higher performance 100-MHz
SDRAM technology. This can be a significant expense for customers, as most workstation
applications require large memory configurations. The Highly Parallel System Architecture, on
the other hand, uses proven EDO memory technology that is supported by other Compaq
enterprise products. Customers who plan to migrate to 100-MHz SDRAM next year will be able
to protect and fully amortize their investment in EDO memory by redeploying the EDO memory
into other systems, such as ProLiant servers and other workstations.