Background
The Digital AlphaStation 255 (AS255), introduced in 1996, was one of Digital Equipment Corporation’s entry-to-midrange 64-bit workstations. In particular, the AlphaStation 255/233 was positioned as a versatile desktop system for engineers, developers, CAD users, and multimedia work, combining DEC’s Alpha architecture with PCI expansion, integrated networking, and support for three major operating environments of the era: Digital UNIX, OpenVMS, and Windows NT.
It used the Alpha 21064A processor at 233 MHz, a 64-bit RISC CPU that gave the machine a distinctly workstation-class identity at a time when many desktop systems were still tied to slower and narrower architectures. In the November 1996 Digital Systems and Options Catalog, DEC quoted performance of 3.80 SPECint95 and 5.09 SPECfp95 for the 255/233, placing it comfortably in the technical workstation conversation of the mid-1990s. The same catalog positioned the 255/233 for 2D CAD, CASE, multimedia, and software development workloads.
Architecturally, the AlphaStation 255 was built around a PCI-based design instead of a proprietary expansion bus. This meant the machine could use more modern, industry-standard expansions rather than relying on proprietary workstation I/O. DEC highlighted the system’s 132 MB/s PCI I/O bus, making it suitable for graphics cards, SCSI adapters, and networking options. The 255 family also included a 128-bit memory bus and 1 MB of onboard secondary cache, helping the 233 MHz processor avoid becoming starved for data.
Physically, the machine came in a compact desktop enclosure, horizontally oriented, with room for internal storage and expansion. Standard features included integrated 10Base-T Ethernet, audio, headphone and microphone jacks, two serial ports, one bidirectional parallel port, keyboard and mouse ports, and an external SCSI-2 connector. The user guide also notes the rear RJ45 twisted-pair Ethernet connection, with optional ThinWire support via the PBXDC-DA media adapter unit. That combination reflects the era well: DEC was clearly trying to make the AlphaStation 255 practical in both office and engineering-network settings.
Storage was typical for a mid-1990s professional workstation but flexible enough to matter. The machine provided four storage slots: one for a floppy drive, one 5.25-inch removable-media bay typically occupied by a 600 MB CD-ROM, and two 3.5-inch hard disk bays. Standard disks in catalog configurations ranged from 1 GB to 2 GB, while optional internal drives went up to 4.3 GB. The integrated controller was a PCI-based Fast Narrow Single-Ended SCSI-2 controller with DMA, and DEC supported additional internal and external SCSI devices, with more controller options available for larger storage setups.
Restoration
The machine was in very good shape when it arrived, only a basic cleaning was required and replacing the coin cell battery on the mainboard. However, the CD-Rom drive had suffered some damage in shipping, which made the eject mechanism misbehaving. It turned out to be a mechanical problem with the optical assembly that had come out of its guide rails. Once indentified, this was an easy fix, and some lithium grease on the moving parts made it work smoothly again.
OS: OpenVMS
Part of the reason why this machine was acquired is that it is capable of running digital’s VMS (as well as Windows NT and Tru64 Unix) which was something missing from the collection after an earlier VaxStation 3100 had been sold due to a move.
VMS development started in 1977 by Digital Equipment Corp. to exploit the virtual addressing capability of the VAX line of computers – after all, VAX stood for “Virtual Addressing eXtension” – which was an important feature for multiuser, multiprocessing computing. Virtual addressing maps each programs logical address space into the physical addressing space, thereby isolating processes from each other and allowing swapping out unused memory pages. Hence the OS name: “Virtual Memory System” (VMS). It was the hot topic of the 80s, IBM named their mainframe OS which also supported virtual memory MVS – Multiple Virtual Storage.
With the introduction of DECs Alpha CPU as a replacement of the older VAX cpus, VMS was ported to the new platform and renamed to OpenVMS to reflect its ability to run on VAX and Alpha processors. Later ports were made to support Intel Itanium and x86-64.
Today, OpenVMS is being maintained and developed by VSI (VMS Software Inc.), who licensed the codebase from Hewlett-Packard in 2014. HP acquired Compaq in 2002 who in turn bought DEC in 1998.
VSI provides enthusiasts two options for running OpenVMS: a virtual machine image for x86 computers and an “Ambassador License” enabling to install the current VMS version (8.4 2L1 at the time of writing) on a physical Alpha machine.
Installing OpenVMS 8.4 on the AlphaStation 255 is supported as per the official documentation and it is relatively straightforward: Burn the OS image to a CD-R, pop it into the drive and run “boot -flags 0,0 dka400” which starts the installer from the CD.
The installation process is well documented in the VSI manuals, basically a number of questions are being asked for which sensible defaults are provided. As part of the installation, the ambassador license key as provided by VSI is required, which will be valid for one year.
There was one glitch that happened during the installation: a file named HELPLIB.HLB was not found, but simply ignoring this error allows the process to finish successfully.
After installation is complete, the machine will boot into the DECWindows graphical environment, which is very similar – if not identical – to the Common Desktop Environment (CDE) that many workstation vendors embraced at the time.
Technical brief: AlphaStation 255/233
| Item | Specification |
|---|---|
| Model | Digital AlphaStation 255/233 |
| Introduction | March 1996 |
| CPU | DEC Alpha 21064A (EV45), 233 MHz |
| Architecture | 64-bit RISC workstation |
| Secondary cache | 1 MB onboard |
| Primary cache | 16 KB instruction + 16 KB data |
| Memory | 32 MB minimum typical, up to 512 MB parity RAM |
| Memory bus | 128-bit |
| Expansion slots | 2 PCI, 1 PCI/ISA combo, 1 ISA |
| PCI bandwidth | 132 MB/s |
| Storage bays | 4 total: floppy, 5.25-inch removable-media bay, 2 × 3.5-inch HDD bays |
| Standard removable media | 600 MB CD-ROM |
| Internal storage examples | 1 GB or 2 GB standard; options up to 4.3 GB |
| Storage controller | Integrated PCI Fast Narrow SCSI-2 with DMA |
| Networking | Integrated 10Base-T Ethernet; optional ThinWire MAU |
| Audio | Integrated audio with headphone and microphone jacks |
| External ports | 2 serial, 1 parallel, keyboard, mouse, external SCSI |
| Supported OS | Digital UNIX V3.2D, OpenVMS V6.2-1H1, Windows NT Workstation 3.51 |
| Typical graphics options | PowerStorm 3D10, 3D30, 4D20, ZLXp-L1, ZLXp-L2 |
| DEC-rated performance | 3.80 SPECint95 / 5.09 SPECfp95 |
| Warranty | 3 years for AlphaStation 255 family according to DEC product description |
| Price in 1996 (w. entry graphics) | USD 7,387 equivalent to $15,316.59 in 2026 |
Links and References
VMS Software: Website
AlphaStation 255 system overview
DEC Systems and Options Catalog, Nov 1996
Digital AlphaStation™ 255 Family User Information
