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System Overview
Introduction
This chapter provides an overview of the Digital AlphaStation 255 system. Topics
covered include the system's new energy-management feature as well as hardware
components, including the motherboard, PCI (peripheral component interconnect)
architecture, front panel, rear panel, system unit components, and keyboard.
Energy Management
Digital AlphaStation 255 systems include a new power-management feature. This feature
ensures that, when the system is idle, it uses significantly less power. (Details on power-
management hardware capabilities of the family of 255 systems are available in the Digital
Alphastation 255 Family Technical Information.)
System Features
Your Digital AlphaStation 255 system uses a high-performance DECchip 21064A CPU
(central processing unit). System features include:
• Memory (DRAM): Up to 1 GB (gigabyte) DRAM
• Primary cache: 16-KB instruction cache and 16-KB data cache on chip.
• Secondary cache: 1 MB.
• Data path: a 132-bit-wide (128 bits of data plus 4 bits of parity) data bus.
• PCI bus adapter with a 32-bit wide multiplexed address/data bus.
• Floppy disk controller.
• Two front-accessible I/O bays: one for 3.5 by 1-inch floppy and one for 5.25 by 1.6-
inch CD-ROM/tape drive.
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