Compaq AlphaServer DS20 Manual de usuario descargar pdf (Pagina 7)

Memory

The switch interconnect can move a large amount of data over

two independent memory data buses. Each memory bus is 256

bits wide (32 bytes). The memory bus speed is 83 MHz. This

yields 2.67 GB/sec bandwidth per bus (32 x 83 MHz = 2.6

GB/sec). With two CPUs the bandwidth becomes 5.2 GB/sec.

Memory throughput in this system is maximized by the

following features:

• Two 256-bit wide memory data buses

• Very low memory latency (120 ns) and high bandwidth

with 12 ns clock

• Numerous reliability and availability features, such as

ECC memory and command/address parity

Memory Options

Each memory option consists of four 200-pin DIMM modules.

The DIMMs are synchronous DRAMs. Each system supports

up to four memory options (16 DIMMs) for a total of 4

gigabytes of memory. The options run at a speed of 83 MHz.

Memory options are supported in the following sizes:

• 256 Mbytes

• 512 Mbytes

• 1 Gbyte

Memory Configuration Rules

• A memory option consists of four DIMMs, and all four

DIMMs must be the same size.

• Convention places the largest memory option in slots

marked 0 on the system board.

• Other memory options can be the same size or smaller

than the first memory option.

• Memory options must be installed in slots designated for

each bank. The first bank goes into slots marked 0, the

second bank into slots marked 1, and so on.

System I/O

There are two 64-bit PCI buses. Industry-standard PCI I/O

buses allow you to use inexpensive, widely available I/O

options. Both 32-bit and 64-bit PCI options can be used.

Six slots can be used for PCI controllers, or five slots for PCI

and one slot for an ISA option.

PCI Bus

The industry-standard PCI bus is the number one choice for

high-performance I/O options, such as disk storage and high-

performance video applications.

The PCI bus implementation has the following characteristics:

• Fully compliant with the PCI Version 2.1 Specification

• Operates at 33 MHz, delivering a peak bandwidth of 500

MB/sec; over 250 Mbytes/sec for each PCI bus

• Supports 6 option slots

• Supports peer-to-peer I/O operations

• Supports three address spaces: PCI I/O, PCI memory, and

PCI configuration space

• Supports byte/word, tri-byte, and longword operations

• Exists in noncached address space only

The Adaptec 7895 chip provides the bridge from PCI to SCSI,

providing for support of an internal tape drive.

ISA Bus

The ISA bus provides system support functions and the use of

peripheral devices. An ISA connector is available for devices

that provide functions not offered in a PCI implementation.

The Cypress SIO chip, which provides the bridge between the

PCI bus and the ISA bus, incorporates the logic for the

following:

• ISA interrupt controller

• Speaker driver

• Decoding and control for utility bus peripheral devices

• IDE interface for CD-ROM (no other IDE devices are

supported)

I/O Configuration Rules

A graphics adapter, if present in the system, must be installed

in PCI 0.

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