Digital Computers

This section encompasses general purpose programmable arithmetic-logic systems of various types, including minicomputers, workstations, programmable logic controllers and small systems.

Rockwell AIM-65
 Rockwell AIM-65

The Rockwell R6500 Advanced Interactive Microcomputer, better known as the AIM-65, is a 6502-based single-board development computer introduced in 1978. The AIM-65 is based on the same architecture as the original MOS Technology KIM-1 6502 development system, introduced in 1976. The AIM-65 features an on-board 20-digit single line alphanumeric LED display and thermal printer, and a detachable QWERTY keyboard mounted on a separate PCB. The AIM-65 supports a number of different language ROMS, including assembler, BASIC, FORTH, Pascal and Rockwell's proprietary PL/65 language, derived from ALGOL and PL/I.

The unit pictured here is a Revision 5 AIM-65, manufactured under license by Dynatem after Rockwell ceased production. The Dynatem AIM-65 has a number of minor differences, including support for newer RAM and ROM IC types which became available over the production lifespan of the AIM-65. The Dynatem AIM-65 is extremely rare.

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Computer Operations CO-4420 Serial Box
 Computer Operations CO-4420 Serial Box

The CO-4420 Serial Box is a ruggedized portable ASR computer terminal with an integral LINC Tape / DECtape style drive, housed in a Halliburton Zero Centurion Elite suitcase. The CO-4420 supports RS-232 and current loop interfaces, and features a one-line 40-character alphanumeric VFD. Computer Operations also manufactured the CO-4410, which omits the display and keyboard featured in the CO-4420.

Computer Operations is best known among computer historians for their range of LINC Tape drives, widely used in the 1960s with DEC and Data General systems. The CO-600 is the most iconic model, featuring dual 'upside down smiley face' drives, the same configuration that was used with the original LINC computer. The Serial Box pictured here features an alternate drive configuration, with a distinctive S-shaped tape guide. This style of drive was also available as a rack-mount peripheral (CO-1005T) for use with contemporaneous minicomputer systems.

Given the production timeframe (circa 1977), it's likely that the CO-4420 is one of the last implementations of the LINC tape drive ever produced. The unit pictured here was manufactured in 1980, and is currently the only known example of a CO-4420 system still in existence.

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Allen Systems FX-97
 Allen Systems FX-97

The Allen Systems FX-97 is an obscure single-board computer based on the 8097, a 16/32-bit embedded microcontroller in Intel's MCS-96 device family. MCS-96 microcontrollers are derived from the earlier 8061, a processor originally designed for the Ford EEC-IV family of engine controllers.

Special thanks to Victor Rizzardi for donating this computer.

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Applied Microsystems EM-188
 Applied Microsystems EM-188

The Applied Microsystems EM-188 is an in-circuit diagnostic emulator for Intel 8080 and 8085 systems. The EM-188 can emulate either the 8080A/8080A-1/8080A-2 or 8085A/8085A-2 microprocessors, requiring two separate emulator probes to support both devices. The most basic function of the EM-188 is to emulate the target system's microprocessor, while a 251x32 bit trace memory captures information from each bus cycle. The trace memory records 16 address bits, 8 data bits, CPU read/write cycles, and the type of bus signal.

The information captured by the trace memory allows the user to examine or alter the microprocessor's register contents, memory locations and I/O ports, and automatically generate breakpoints based on specified conditions. The EM-188 has two independent address comparators which constantly monitor the target microprocessor's address bus. Each comparator may be set to generate a breakpoint on read and/or write cycles, as well as memory and I/O addresses. The comparators can also be configured interactively to generate a breakpoint based on sequential conditions or a range of address values. Additionally, the EM-188 has a large selection of preprogrammed diagnostic routines.

Applied Microsystems manufactured a number of similar emulator products for different microprocessors. EM-184 and EM-180 emulate the Zilog Z80, EM-186 emulates the Motorola 6800, EM-189 emulates the Motorola 6809, and EM-149 emulates the MCS-48 family of microcontrollers. The first of these systems was the EM-184, designed by Applied Microsystems founder Robin Knoke in 1979. Later EM-1xx models, derived directly from the EM-184 platform, were designed by engineer Tim Nelson in the early 1980s.

Special thanks to Victor Rizzardi for donating this system.

Applied Microsystems EM-188 Diagnostic Emulator User's Manual (PDF)
Applied Microsystems U.S. Price List 04/1983 (PDF)

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Texas Instruments Silent 700 Model 745
 Texas Instruments Silent 700 Model 745

The TI Silent 700 Model 745 Portable Data Terminal is a late-model 300 baud KSR teletypewriter, built upon the Intel 8080 microprocessor. The Model 745 has an integrated acoustic coupler modem and serial interface. The Silent 700 line includes ASR, KSR and RO variants, released in several different product generations through the 1970s. All Silent 700 series terminals utilize TI's low-noise thermal printing technology.

Silent 700 terminals were widely adopted and, along with early portable programmable calculators, played a key role in acclimating users to the concept of portable computing, long before true portable computers were technically feasible.

Texas Instruments Silent 700 Model 745 Operating Instructions (PDF)
Texas Instruments Silent 700 Model 743 & 745 Maintenance Manual (PDF)

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Tracor Aerospace AN/UGC-129 Teletypewriter Set
 Tracor Aerospace AN/UGC-129 Teletypewriter Set

Devices included in this entry:

Tracor AN/UGC-129 Teletypewriter Set (pictured in thumbnail)
Tracor MU-734/UGC Teletypewriter Magnetic Tape Unit


The Tracor AN/UGC-129 Teletypewriter Set was the standard U.S. Air Force teletype terminal throughout the 1980s and 1990s. The AN/UGC-129 is a nuclear-hardened, microprocessor-controlled full-duplex teletype with 8K of memory and 120cps printing speed, and is considered suitable for air, land and sea applications. The unit pictured here is the first variant of the AN/UGC-129, equipped with a high speed rotating type head and direct readout. A later, more common variant, the AN/UGC-129(V)1, is virtually identical, but features a conventional dot matrix print head and a 40-character electroluminescent line display. The (V)1 variant can be easily identified by its protruding readout area which overhangs the keyboard.

Among its numerous installations, the AN/UGC-129 was notably an integral component of the Minuteman II ICBM Launch Control Facility.

AN/UGC-129 Teletypewriter Set Operation and Maintenance Instructions (Partial File) (PDF)

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Texas Instruments 5TI
 Texas Instruments 5TI

Devices included in this entry:

Texas Instruments 5TI-1032-1 Sequencer
Texas Instruments 5TI-2001 Programmer (pictured in thumbnail)


The Texas Instruments 5TI is a compact TTL-driven programmable logic controller, designed for industrial automation. A basic system consists of a 5TI-1032 series sequencer, and a 5TI-2000 series programmer.

The 5TI-2001 programmer is a handheld interface for the 5TI-1032-1 sequencer. It allows the operator to temporarily interface with the sequencer and enter program steps. This device does not have a power switch or any provision for using line or battery power; it receives its power from the sequencer, through a permanently attached interface cable. The case of the 5TI is the same as that of the SR-20 scientific calculator, desktop companion of the SR-10 pictured above. However, its similarities to the SR-20 are superficial. The 5TI programmer is built from discrete TTL, implementing 39 TTL ICs in the programmer, and another 39 TTL, static RAM and UV-EPROM ICs in the sequencer itself. The display is a Burroughs Panaplex II with 10+2 digits, similar to the displays used in various TI desktop calculators from the same era.

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Digital Equipment Corporation VAXserver 3500
 Digital Equipment Corporation VAXserver 3500

The DEC VAXserver 3500 is a high end variant in the MicroVAX III series. Codenamed 'Mayfair', the VAXserver 3500 was introduced in September 1987 and makes use of a 11.11MHz CVAX chipset. The CVAX microprocessor is a second-generation single-chip VAX ISA implementation, containing 134,000 transistors on a 9.4 x 7.4mm die, and fabricated using DEC's first-generation CMOS process. The entire CVAX chipset consists of six chips: the CVAX 78034 CPU, CFPA floating-point accelerator, CVAX clock chip, CVAX System Support Chip (CSSC), CVAX Memory Controller (CMCTL), and the CVAX Q-Bus Interface Chip (CQBIC).

Due to DEC's obnoxious software licensing schemes, the VAX 3500 platform was offered in a number of insignificantly different variants. The two key variants are the MicroVAX 3500 and VAXserver 3500, which are virtually identical except for a slight difference in the CPU microcode which determines whether the system can run single-user or multi-user software. A MicroVAX 3500 can be easily converted to a VAXserver 3500, simply by swapping its KA650-AA CPU card for a KA650-BA card.

The VAXserver 3500 is a class of system once referred to as a 'supermini'. Such systems evolved directly from traditional minicomputers of the 1960s and 1970s, but typically featured a 32-bit word, elaborate instruction sets and other advanced characteristics more commonly seen on larger systems.

The original VAX-11/780 is considered to be the definitive supermini; the VAX architecture completely dominated the mid-range computer market for about 15 years, beginning in 1978. This period was marked by a rapid decline in the minicomputer industry, which would ultimately destroy DEC and many other notable minicomputer manufacturers, such as Data General and Prime Computer. The only major minicomputer manufacturer to survive the culling would be Hewlett-Packard, which ultimately devoured the carcasses of its various competitors. The VAXserver 3500 is among the last minicomputers ever built. Beginning in the late 1980s, the mid-range computer market would be taken over by 64-bit RISC servers and desktop workstations, and the minicomputer form factor would be abandoned entirely.

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Hewlett-Packard 2114B
 Hewlett-Packard 2114B

The Hewlett-Packard 2114B computer is a size-reduced, cost-reduced descendant of the original HP 2116A minicomputer. Released in 1969, the HP 2114B is a hard-wired word-addressed 16-bit CPU with a derivative PDP-8 architecture. Its technology primarily consists of SSI TTL integrated circuits and magnetic core memory.

The early HP 2100 series computers are regarded as some of the most reliable computers ever built. Systems often ran continuously for years without failure. They also marked the birth of a CPU architecture that would be adapted and utilized in numerous HP computers, calculators and analyzers over the next two decades.

Core Memories: A Photographic History of Early HP Computers
Hewlett-Packard First Generation Computer Census (last update 2016-07-18)

2114B Brochure (PDF)
2114B Price Sheet 06/1970 (PDF)
2114B Price Sheet 05/1971 (PDF)
2114B Volume 1: Specifications and Basic Operation (PDF)
2114B Volume 2: Operation & Maintenance Manual (PDF)
2114B Volume 3: Input/Output System Operation (PDF)
2116 / 2115 / 2114 Absolute Binary Loader Reference Card (PDF)
12618A Synchronous Data Set Interface Kit (PDF)
12539A Time Base Generator Interface Kit (PDF)

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Hewlett-Packard 2100A
 Hewlett-Packard 2100A

The Hewlett-Packard 2100A is the first iteration of HP's second generation 16-bit minicomputers. The 2100A utilizes the same basic architecture as HP's first generation systems, but is noteworthy as being the first microprogrammable minicomputer, and the first minicomputer with a switching power supply.

The CPU of the HP 2100A and nearly identical HP 2100S are constructed of discrete TTL and CTuL logic ICs, and are the last 2100-series minicomputers manufactured by HP that make use of core memory. The 2100A has a maximum memory capacity of 32K, 14 I/O channels, dual-channel DMA and hardware multiply/divide. Essentially, the 2100A is a maximally upgraded, microprogrammable 2116C, in a chassis less than half the size. The introduction of the 2100A instantly made all previous HP minicomputers obsolete.

Unlike HP's first generation systems, the 2100A entirely omits all register displays (except for the switch register), marking a turning point in the evolution of computers which spread across the entire industry through the 1970s. Without register displays, traditional machine language programming from the front panel would become an impossibility.

The unit pictured here was originally installed as part of a Measurex process control system, and has been re-branded as a Measurex 2650 Central Processing Unit. An internal examination of the computer reveals a custom Measurex circuit card installed in slot A9, a location normally reserved for a genuine HP direct memory access card.

Based in Cupertino CA, Measurex was one of the first companies to develop industrial process control equipment, and their early systems were built around HP 2116 and HP 2100 computers. Measurex was one of HP's largest computer customers, but they had the bad habit of anonymizing or re-branding the HP computers used in their systems. The majority of these early Measurex process control systems were employed in paper mills, a true testament to the near indestructibility of HP's 2100-series minicomputers.

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Hewlett-Packard 21MX / 1000 M-Series
 Hewlett-Packard 21MX / 1000 M-Series

After the 2100A and 2100S, HP released the 21MX series, believed to be the industry's first minicomputers to be equipped with semiconductor RAM. The original 21MX series from 1974 consists of three models of ascending size and expansion capacity: 2105A, 2108A and 2112A.

The 2108B (pictured here) and 2112B were added to the series in 1976, the most notable improvement over the 'A' variants being the relocation of the power switch from the rear of the CPU to a more traditional and accessible location behind the lockable front panel.

In 1976, HP released the improved 21MX E-Series, renaming the original 21MX computers as 21MX M-Series to distinguish them from the E-Series systems. When HP released the third generation of 21MX systems in 1978, the naming convention was changed once again. These new systems were named 1000 F-Series, and the older 21MX systems were renamed as 1000 M-Series and 1000 E-Series to maintain conformity.

1000 M-Series Installation & Service Manual (PDF)

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