MicroVAX
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Predecessor | VAX-11 series (implied) |
| Founded | 1984 |
| Founder | Digital Equipment Corporation (DEC) |
| Successor | VAX 4000 series |
| Products | Minicomputers executing VAX ISA |
| Owner | Digital Equipment Corporation |
The MicroVAX series, now discontinued, comprised a line of cost-effective minicomputers created by Digital Equipment Corporation (DEC). The initial unit, MicroVAX I, debuted in 1984. These systems utilize processors that execute the VAX instruction set architecture (ISA) and were eventually replaced by the VAX 4000 lineup. Numerous MicroVAX models have equivalent VAXstation versions, which incorporate additional graphics processing capabilities. This product family supports Digital's operating systems including VMS, ULTRIX, and VAXELN. Prior to the release of VMS version 5.0, MicroVAX systems required a specialized edition known as MicroVMS.
MicroVAX I
Launched in October 1984 and internally referred to as Seahorse, the MicroVAX I was one of DEC's earliest VAX computers to integrate very-large-scale integration (VLSI) technology. Its central processing unit, the KA610 module (also called KD32), comprises two proprietary chips dedicated to the ALU and FPU, while additional functions are managed by TTL components. Two variants of the floating-point chips exist, supporting distinct instruction sets (F and G, or F and D). The architecture is built upon two quad-height Q-bus cards: a Data Path Module (DAP) paired with a Memory Controller (MCT). Due to limitations inherent to the Q-bus design, memory capacity maxes out at 4MiB. Performance benchmarks rate this system at approximately 0.3 VUPs, aligning it with the earlier VAX-11/730 model.
MicroVAX II
Introduced in May 1985 as a mid-tier offering within the MicroVAX range, the MicroVAX II, code-named Mayflower, succeeded the original MicroVAX and was made available as an upgrade path for existing users. It supports operating systems such as VAX/VMS and DEC's Unix variant, ULTRIX, alongside at least one third-party OS option—BSD Unix provided by mt Xinu.
Engineered to deliver between 70% and 110% of the performance of a VAX-11/780 at a more affordable price point, the MicroVAX II is compatible with all VAX software but initially lacked support for certain peripherals and did not offer VAXcluster functionality at launch. Market analysis by Forrester Research predicted it would outsell older models such as the VAX-11/725, 730, and potentially 750. The system employs the KA630-AA CPU module—a quad-height Q22-Bus component—featuring a 5 MHz MicroVAX 78032 microprocessor paired with a MicroVAX 78132 floating-point coprocessor. This module also includes 1 MB of onboard memory, boot and diagnostic ROMs, a DZ console serial interface, a real-time clock, and DMA transfer controllers.
Memory expansion options range from 1 MB up to 16 MB through zero to two MS630 expansion modules. These modules come in several configurations: 1 MB (MS630-AA), 2 MB (MS630-BA), 4 MB (MS630-BB), and 8 MB (MS630-CA), all utilizing byte-parity protected 256 Kb DRAM chips. Connectivity between these memory expansions and the CPU module is established via the backplane along with a ribbon cable serving as address and data buses.
The MicroVAX II was marketed in three different chassis types:
- BA23
- BA123
- 630QE (designed as a deskside model)
At the same time, DEC introduced the VAXstation II workstation built around the MicroVAX II processor, which replaced the original VAXstation.
Additionally, the Robotron K 1820, produced briefly in East Germany during 1990, is essentially a clone of the MicroVAX II system.
KA620
The KA620 is a single-board MicroVAX II system tailored for automated testing and manufacturing environments, operating exclusively on DEC's real-time VAXELN operating system. A configuration equipped with 1 MB of memory and VAXELN Run-Time Package version 2.3 was priced at approximately US$5,000.
Mira
Developed by DEC's European Centre for Special Systems located in Annecy, France, the Mira represents a fault-tolerant MicroVAX II setup. It incorporates two MicroVAX 78032 microprocessors—one active and one standby—that are interconnected through Ethernet, with software managing automatic failover upon detecting faults.
Industrial VAX 630
This model consists of a MicroVAX II installed within a BA213 chassis.
MicroVAX III
An enhanced MicroVAX model housed in either BA23 or BA123 enclosures, utilizing the KA650 CPU module based on the CVAX chipset.
MicroVAX III+
An upgraded version of the MicroVAX III, featuring the KA655 CPU module within a similar chassis.
VAX 4
A MicroVAX system placed in BA23 or BA123 enclosures, upgraded with the KA660 CPU module.
MicroVAX 2000
Launched on 10 February 1987 under the codename TeamMate, the MicroVAX 2000 targeted budget-conscious segments such as academic institutions and remote VAX developers. It employs the same microprocessor and floating-point coprocessor as the MicroVAX II but with cost-saving reductions like a maximum memory capacity of 14 MB (compared to 16 MB) and absence of Q-Bus expansion slots. Storage options include Shugart-compatible hard drives (ST412 interface with MFM encoding) alongside an integrated 5.25-inch RX33 floppy drive. Supported operating systems encompass both VMS and ULTRIX. The device features a compact desktop design.
MicroVAX 3100 Series
Introduced in 1987, this series comprises models encased in desktop-style enclosures:
- MicroVAX 3100 Model 10
- Teammate II
- Equipped with KA41-A CPU module featuring CVAX chipset running at 11.11 MHz (90 ns cycle time)
- MicroVAX 3100 Model 10e
- Teammate II
- Utilizes KA41-D CPU module with CVAX+ chipset clocked at 16.67 MHz (60 ns)
- Supports up to 32 MB RAM
- MicroVAX 3100 Model 20
- Teammate II
- Same KA41-A CVAX processor at 11.11 MHz (90 ns) as Model 10
- Presented in an enlarged enclosure
- MicroVAX 3100 Model 20e
- Teammate II
- Features KA41-D CVAX+ CPU running at 16.67 MHz (60 ns)
- Model 10e configuration housed in a larger case
- MicroVAX 3100 Model 30
- Waverley/S
- Entry-level design developed in Ayr, Scotland; released October 1993
- Powered by KA45 SOC CVAX processor at 25 MHz (40 ns)
- Maximum memory capacity of 32 MB
- MicroVAX 3100 Model 40
- Waverley/S
- Also developed in Ayr and introduced October 1993
- Equipped with KA45 SOC running at 25 MHz (40 ns)
- Memory ranges from 8 to 32 MB; larger enclosure than Model 30
- MicroVAX 3100 Model 80
- Waverley/M
- Ayr-origin entry-level model debuted October 1993
- Incorporates KA47 Mariah NVAX processor at 50 MHz (20 ns) with a 256 KB external cache
- Maximum RAM supported is 72 MB
- MicroVAX 3100 Model 85
- Waverley/M+
- Released August 1994
- Powered by KA55 NVAX CPU running at 62.5 MHz (16 ns), featuring a 128 KB external cache
- Memory capacity between 16 and128 MB
- MicroVAX 3100 Model 88
- Waverley/M+
- Introduced October1996; last orders accepted September2000, final shipments December2000
- Uses KA58 NVAX processor clocked at62.5 MHz (16 ns) with128 KB cache
- Supports from64 to512 MB RAM
- MicroVAX 3100 Model90
- Cheetah
- Began shipping October1993; shares architecture with VAX4000 Model100 but replaces DSSI storage with SCSI interface
- Powered by KA50 NVAX CPU at72 MHz (14 ns), equipped with128 KB cache
- Maximum memory size is128 MB
- MicroVAX3100Model95
- Cheetah+
- Released April1994
- Features KA51 NVAX processor running at83.34 MHz (12 ns) with512 KB cache
- MicroVAX3100Model96
- Cheetah++
- Fitted with KA56 NVAX CPU operating at100 MHz(10 ns)
- Memory ranges from16 to128 MB
- MicroVAX3100Model98
- Cheetah++
- Began production October1996; last order date September2000, last shipment December2000
- Includes KA59 NVAX processor at100 MHz(10 ns) and512 KB cache
- InfoServer100/150/1000
- A versatile storage server linked to the MicroVAX3100 Model10 line, running specialized firmware powered by a KA41-C CPU module
MicroVAX 3500 and MicroVAX 3600
Released in September 1987, the MicroVAX 3500 and 3600, internally designated as Mayfair, represented the premium tier within the MicroVAX series. These systems offered performance exceeding three times that of the MicroVAX II and accommodated up to 32 MB of ECC main memory, doubling the capacity of earlier models. The enhanced speed was achieved through the use of the 11.11 MHz (90 ns cycle) CVAX chipset combined with a two-level, write-through cache design. Both models incorporated the KA650 CPU module.
MicroVAX 3300 and MicroVAX 3400
Unveiled on 19 October 1988, the MicroVAX 3300 and 3400, referred to as Mayfair II, were designed to serve entry-level to mid-range server markets, positioning DEC against IBM’s AS/400. These systems employed the KA640 CPU module, enabling DEC to compete effectively within business computing segments.
MicroVAX 3800 and MicroVAX 3900
Introduced in April 1989, the MicroVAX 3800 and 3900, also known as Mayfair III, acted as advanced successors to the 3500 and 3600 models, directly rivaling IBM’s AS/400. Their launch prices were US$81,000 for the 3800 and US$120,200 for the 3900. The rtVAX 3800 variant was specifically aimed at real-time computing environments such as computer-aided manufacturing (CAM). Both systems featured the KA655 CPU module with a 16.67 MHz (60 ns cycle) CVAX chipset and supported up to 64 MB of memory.