DECpc AXP 150

Digital Equipment Corporation
Industry	Computer hardware
Founded	November 8, 1957; 69 years ago
Headquarters	Maynard, United States
Products	DECpc AXP 150, DEC 2000 AXP series (Model 300, Model 500)

The DECpc AXP 150, internally referred to as Jensen, represents a low-tier workstation created by Digital Equipment Corporation. Introduced on 25 May 1993, it was the inaugural Alpha-based platform compatible with the Windows NT operating system and laid the groundwork for the DEC 2000 AXP line of entry-level servers. Production ceased on 28 February 1994, with the device being replaced by the entry-level Multia and subsequent models within the AlphaStation series. The design and manufacturing processes were overseen by Digital's Entry Level Solutions Business located in Ayr, Scotland.

DEC 2000 AXP

The DEC 2000 AXP series consists of entry-level servers evolved from the DECpc AXP 150, incorporating support for Digital's OpenVMS AXP and OSF/1 AXP (later known as Digital UNIX) operating systems, along with compatibility for VT-series terminals. This server family was eventually replaced by the AlphaServer 1000, which included two variants: Model 300 and Model 500.

Model 300

Known by the code name Jensen, the DEC 2000 Model 300 AXP is essentially a DECpc AXP 150 adapted for server use. Launched on 12 October 1993, it omitted certain workstation features and was discontinued on 28 February 1994.

Model 500

Designated Culzean, the DEC 2000 Model 500 AXP targeted server deployments running Windows NT Advanced Server, DEC OSF/1 AXP, or OpenVMS. Released on 15 November 1993, this model featured a larger pedestal chassis capable of housing up to twelve 3.5-inch hard disks and included an Intelligent Front Panel (IFP) for real-time system monitoring. Power configurations offered either dual 415 W power supplies or a combination of one supply plus a battery-backed Standby Power Supply (SPS). The Model 500 was withdrawn from the market on 30 December 1994.

Description

At its core, the DECpc AXP 150 employed a 150 MHz DECchip 21064 microprocessor paired with an external Level 2 cache of 512 KB implemented using high-speed SRAM chips mounted on the motherboard.

Its memory architecture featured a wide 128-bit subsystem supporting between 16 and 128 MB of parity-protected SIMMs across eight slots arranged into two banks. The DEC 2000 AXP provided two memory upgrade kits: one comprising four 4 MB SIMMs totaling 16 MB, and another consisting of four 16 MB SIMMs totaling 64 MB.

Expansion capabilities included six EISA slots commonly equipped with peripherals such as a Compaq QVision VGA graphics card, an Adaptec AHA-1742 SCSI host adapter, and a DEC DE422 Ethernet network card. Designed primarily as a Windows NT workstation, it supported VGA display output exclusively.

In contrast to other Alpha platforms like the DEC 3000 AXP, which utilized Digital's proprietary TURBOchannel bus, the DECpc AXP 150 incorporated the industry-standard EISA bus to reduce expenses and broaden third-party hardware compatibility. While TURBOchannel delivered superior performance, it required costly ASICs and had limited vendor support.

Because the signaling protocol of the DECchip was incompatible with EISA peripherals directly, signals were translated into two "pseudo-486" buses—one carrying address and command signals and another providing a full-width 32-bit data path—emulating Intel 80486 interfaces. The EISA bus itself was implemented using Intel’s 82350DT chipset components, including bus controllers and buffers that interfaced with these pseudo-486 buses.

This intricate bus translation resulted in a less efficient input/output subsystem, restricting maximum EISA bus throughput to approximately 25 MB/s compared to typical PC rates of around 33 MB/s.

A VLSI Technologies VL82C106 integrated circuit connected to these buses combined several functions: a real-time clock, battery-backed RAM for storing system configuration data, two serial communication ports, one parallel port, and dual PS/2 connectors. The battery-backed RAM received power from an external battery pack to maintain data retention.

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