The Complete Guide to VAX Computer Systems: History, Features, and Future

What are VAX Computer Systems?

VAX stands for Virtual Address eXtension. VAX computer systems refer to a series of 32-bit minicomputers designed by DEC or Digital Equipment Corporation. Simply put, VAX is the hardware, and DEC is the company that produced VAX. The series started with the VAX-11/780 in 1977 – the first commercially successful model.

VAX computers primarily ran the VAX/VMS operating system, which later evolved into OpenVMS. In modern days, the use of this OS is very niche, particularly used by organizations to run mission-critical legacy workloads.

VAX computers were produced for over a decade, with the final model launched in the early 1990s. After that, DEC moved on to a new system. The successor to VAX was called DEC Alpha.

These machines were significant in computing history. They bridged the gap between early minicomputers and more advanced systems. VAX’s long production run demonstrates its impact on the industry.

Originally, VAX computers were made for the science and engineering world. Early on in the 1980s, they were also used for accounting and finance.

The VAX architecture was built on a CISC design, featuring a variable-length instruction format and a wide range of addressing modes. It has a highly orthogonal instruction set architecture. It also includes complex operations such as queue insertion or deletion, number formatting, and polynomial evaluation.

6 Key Features of VAX Architectures

DEC VAX was one of the first commercially successful computers to implement virtual memory.

1. Virtual Memory

DEC VAX was one of the first commercially successful computers to implement virtual memory.

What is virtual memory?

A method of employing secondary storage (such as disk or SSD memory, etc.) as main memory. This allowed a user to build and run a program that required more memory than the limited quantities of main memory available at the time. With the help of virtual memory, VAX computer systems can use secondary storage as if it were the primary storage.

VAX computers split their virtual memory into four parts. Each part was one gigabyte in size. These sections were used for different purposes: user processes, process stacks, and the operating system. This division made memory management more efficient. It also kept processes separate from each other.

This virtual memory feature enabled users to run tasks that seemed impossible to execute. It made writing programs easier because programmers didn’t have to divide them into segments to fit the limited memory available at the time.

2. CISC Design

The VAX architecture is a classic example of the Complex Instruction Set Computing (CISC) design. Hence, they have a rich, complex instruction set that allows for the efficient execution of various operations.

Also, VAX computer systems use variable-length instruction formats that support numerous addressing modes. Such flexibility enhances the system’s task-handling capabilities. The architecture features 16 general-purpose registers that are labeled R0 to R15. Some have special uses, like the Argument Pointer and Stack Pointer. This setup aids in efficient memory management.

3. Data Types and Formats

The VAX computer supports various data types and formats, including:

• Integers: Stored as binary numbers in byte, word, longword, quadword, or octaword formats.
• Characters: Represented using 8-bit ASCII codes.
• Floating Points: Four different floating-point formats are used to represent this. Starting from 4 to 16 bytes in length.

4. Instruction Sets

VAX instructions are designed to be independent, which is called orthogonality. It means that any addressing mode can be used with any instruction. This flexibility comes from a variable-length instruction format and various addressing modes, such as register mode, autoincrement, autodecrement, and base relative addressing.

The registers have special roles, like the Stack Pointer. The system handles various data types, including integers, characters, and floating-point numbers.

VAX instruction mnemonics combine different elements to create a wide range of operations, such as:

• Prefix, which defines the type of the operation
• Suffix, which reflects the data types
• Modifier, which reflects the number of operands involved.

Also, register masks are a standout feature. They’re at the start of each subprogram. They show which registers to save and restore.

5. Input/Output (I/O) Implementation

VAX architecture handles input and output through special controllers. These I/O device controllers are key to managing data flow, with each having its own set of registers that are used for control and status monitoring.

The VAX system maps these registers into a specific area. This area is called I/O space. It’s a part of the overall address space. By doing this, the CPU can easily interact with I/O devices, making the I/O management more efficient. This approach streamlines communication between the CPU and peripherals.

6. Addressing Modes of VAX Computers

Addressing modes determine how the system finds data in memory, which enables flexibility and efficient memory access.

• In Register Mode, the data is directly in the register. The instruction simply points to the correct register.
• Register-Deferred Mode is different. Here, the register holds the address of the data, not the data itself.
• In Autoincrement Mode, the register value increases after use. Autodecrement Mode decreases the value before use.
• Autoincrement Deferred Mode is similar but always increases by 4.
• Displacement Modes use a base register and an extra value. This combination calculates the final address. The extra part can be a byte, word, or longword.
• Immediate and Literal Modes put the data right in the instructions.
• Indexed Mode is useful for arrays. It uses a base and an index to find data.
• PC-Relative Mode uses the program counter to locate data.
• Absolute Mode simply states the address directly.

Hardware Developments and Evolution of VAX Computers

The VAX hardware evolved significantly over time. Let us look at the important developments:

Use Cases of VAX Computers Across Different Industries

Now that you have an idea about the key essentials of VAX computer systems, let us shed light on its industry-specific applications.

Federal Research and Government

VAX computer systems were crucial in government operations. They excelled in scientific computing, data analysis, and simulations. The Naval Surface Warfare Center used them for submarine dynamics simulations. At the Energy Department’s Combustion Research Facility, VAX computers aided combustion engine experiments. They also processed Army vehicle simulations.

Engineering and Scientific Applications

Engineers relied on VAX for CAD, simulations, and modeling. These machines handled large datasets with ease. They became the go-to for scientific and engineering research. VAX computers supported various applications, from radar processing to flight control systems.

Business and Financial Services

Businesses embraced VAX for operational needs. They used them for database management and transaction processing. VAX’s multitasking capabilities boosted productivity. Companies ran multiple applications simultaneously. Office automation tasks like word processing and email also benefited from VAX computers.

Education and Academia

VAX computers were staples in educational institutions. They supported research and teaching and served as access points for students and faculty. Universities used them for programming courses and research projects. VAX’s reliability made it a valuable academic resource.

Telecommunications

The telecom industry leveraged VAX for network management. These systems excelled at handling multiple connections and processes. VAX played a key role in developing and maintaining telecommunications infrastructure.

Healthcare

Hospitals and clinics use VAX for patient records and scheduling. The system’s reliability streamlined healthcare operations. VAX provided a robust platform for healthcare administration and improved patient care efficiency.

Advantages of VAX Computers

Back in its heyday, VAX computer systems were renowned for their unique advantages. Let us look at them all.

Backward Compatibility

VAX computer systems maintained compatibility with PDP-11. This feature protected existing software investments. Users could upgrade while keeping their familiar programs.

Versatile Instruction Set

VAX computers used a complex instruction set computer (CISC) design. Its assembly language was user-friendly. Its assembly language was user-friendly. The instruction set was powerful and orthogonal, which in turn, made it popular among programmers.

Advanced Memory Management

VAX introduced sophisticated virtual memory management. It divided virtual memory into four 1GB sections. This design allowed for efficient multitasking and memory use.

Cost-Effective Performance

VAX systems rivaled mainframes at a fraction of the cost. They could address over 4GB of virtual memory. This capacity far exceeded most minicomputers of the time.

Model Variety and Compatibility

The VAX family included ten designs and over 100 models. All were compatible with each other. Most of them ran on the VAX/VMS operating system (later came out as OpenVMS OS). This variety gave users flexibility in choosing systems.

Reliability and Low Maintenance

VAX computers were known for their dependability. They had lower operating and maintenance costs. This made them attractive to businesses and institutions.

Software Development

Impact VAX systems played a crucial role in PC software development. They provided a robust platform for UNIX and C software. VAX computers offered higher throughput than PDP-11/70 for UNIX operations.

The Challenges with VAX Hardware

While once revolutionary, VAX hardware now presents significant challenges. What’s more alarming is that these challenges can lead to business failure.

When talking about challenges, the most threatening one is downtime. It hinders your business operation and costs you extensively. In fact, data suggests that for small businesses, the average cost of downtime is around £7000 per hour.

Also, the hardware has reached end-of-life, which means it’s no longer being produced. So, finding support and replacement parts is a cumbersome task. Again, the old hardware consumes a lot of power, which leads to higher energy consumption bills.

Overall, the hardware can fail at any time. And when it does, companies end up regretting that they should have planned earlier.

Modernize VAX Computer Systems with Stromasys

Thanks to emulation, enterprises can protect themselves from the severe threats of vintage DEC hardware and still run their legacy application.

Stromasys has solved this problem with Charon-VAX. With our emulator, you can easily run your VAX/VMS operating systems seamlessly – only the underlying hardware will be replaced with an on-premise or on-cloud platform. No risky migration process. No coding required. Our forte lies in a simple lift and shift emulation. Enjoy the benefits of a reliable and efficient hardware infrastructure by paying a fraction of the cost of maintaining the age-old hardware.