Specifications

1–4 Introduction 9 March 1999 – Subject To Change
System Components and Features
1.1.3 L3 Bcache Subsystem Overview
The AlphaPC 164LX board-level L3 backup cache (Bcache) is a 2MB, direct-
mapped, synchronous SRAM with a 128-bit data path. The board is capable of han-
dling an L3 cache size of 4MB. See Section 2.3 for more information about the
Bcache.
1.1.4 PCI Interface Overview
The AlphaPC 164LX PCI interface is the main I/O bus for the majority of functions
(SCSI interface, graphics accelerator, and so on). The PCI interface has a 33-MHz
data transfer rate. PCI-IDE support is provided by an onboard controller chip
(CMD646). An onboard PCI-to-ISA bridge is provided through an Intel 82378ZB
Saturn-I/O (SIO) chip.
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 FDC37C935 combination controller chip that provides:
– A mouse and keyboard controller
– A diskette controller
– Two universal asynchronous receiver-transmitters (UARTs) with full modem
control
– A bidirectional parallel port
– A time-of-year (TOY) clock
• Operating system support—through a 1MB flash ROM that contains supporting
firmware.
1.1.6 Miscellaneous Logic
The AlphaPC 164LX contains the following miscellaneous components:
• Synthesizer for clocks:
– A clock synthesizer (MC12439) provides a programmable 466-, 533-, and
600-MHz clock source to the 21164 microprocessor. The microprocessor
supplies a clock to the system PLL/clock buffer for the 21174.