Specifications

17 January 1997 – Subject to Change
Introduction to the AlphaPC 164 Motherboard 1–3
System Components and Features
1.1.1 Digital Semiconductor 21172 Core Logic Chipset
The 21164 microprocessor is supported by the 21172 core logic chipset. The chipset
consists of the following two application-specific integrated circuit (ASIC) types:
•
One copy of the Digital Semiconductor 21172-CA control, I/O interface, and
address (CIA) chip provides the interface between the 21164 microprocessor,
main memory (addressing and control), and the PCI bus. It also provides the
companion data switch chips with control information to direct the data flow.
•
Four copies of the Digital Semiconductor 21172-BA data switch (DSW) chip
provide the memory interface data path and route PCI data through the CIA chip.
The chipset includes the majority of functions required to develop a high-
performance PC or workstation, requiring minimum discrete logic on the module. It
provides flexible and generic functions to allow its use in a wide range of systems.
1.1.2 Memory Subsystem
The dynamic random-access memory (DRAM) is contained in one bank of single
inline memory modules (SIMMs). Single- or double-sided SIMMs may be used.
Each SIMM is 36 bits wide, with 32 data bits and 4 check bits, with 70 ns or less
access. Four SIMMs fill a data bus width of 128 bits and provide 16MB to 256MB.
Eight SIMMs fill a data bus width of 256 bits and provide 32MB to 512MB.
Table 1–1 lists the SIMM sizes supported and the corresponding main memory size
for 256-bit arrays.