Specifications

1–4 Introduction 26 November 1997 – Subject To Change
System Components and Features
1.1.3 L2 Bcache Subsystem Overview
The AlphaPC 164SX board-level L2 backup cache (Bcache) is a 1MB, direct-
mapped, synchronous, pipelined burst SROM with a 128-bit data path. The board is
capable of handling an L2 cache size of 2MB. See Section 2.3 for more information
about the Bcache.
1.1.4 PCI Interface Overview
The AlphaPC 164SX PCI interface, with a 33-MHz data transfer rate, is the main
I/O bus for the majority of functions (SCSI interface, graphics accelerator, and so
on). PCI-EIDE support is provided by an onboard controller chip (Cypress
CY82C693U-NC), which also provides a PCI-to-ISA bridge, a mouse and keyboard
controller, and a time-of-year (TOY) clock.
The PCI bus has four dedicated PCI expansion slots (two 64-bit and two 32-bit).
1.1.5 ISA Interface Overview
The ISA bus provides the following system support functions:
• Two expansion slots.
• An SMC FDC37C669 combination controller chip that provides:
– A diskette controller
– Two universal asynchronous receiver-transmitters (UARTs) with full
modem control
– A bidirectional parallel port
1.1.6 Miscellaneous Logic
The AlphaPC 164SX contains the following miscellaneous components:
• Operating system support — through a 1MB flash ROM that contains supporting
firmware.
• Synthesizer for clocks:
– A clock synthesizer (MC12439) provides a programmable 400- and
533-MHz clock source to the 21164PC microprocessor. The microproces-
sor supplies a clock to the system PLL/clock buffer for the 21174.
– The 21174 core logic chip provides the SDRAM and PCI clocks.