HP 2100

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The HP 2100 was a series of minicomputers produced by Hewlett-Packard's from the late 1960s to early 1980s. The 2100 was also a specific model in this series. The series would be renamed to HP 1000 by the 1970s and sold as real-time computers complementing the more complex IT-oriented HP 3000. They would eventually be phased out in favor of UNIX-based RISC workstations.

The 2116A, the first model of the series, was developed in the late 1960s. It was not designed by HP, but bought from another firm. It was a 16-bit word-addressed general purpose computer. Main memory was 4096 words (4K), expandable to 32K of magnetic core. The memory cycle time was 1.6 microseconds.

Contents 1 2100 series architechture 2 Descendents and variants 3 Instruction overview 4 Model overview 4.1 Early models (1966-1969) 4.2 Second generation (1970-1974) 4.3 21MX (1975-????) 4.4 Operating System 4.5 Introduction dates 5 References

2100 series architechture

There were two 16-bit accumulators, called A and B and two 1-bit flags, called Overflow and Extend. The program counter, 15 bits, was called P. All instructions in the standard instruction set were 16 bits long. As with the roughly-contemporaneous PDP-8 from DEC, memory was word (not byte) accessible and conditional branching was done with a conditional skip followed by a jump instruction.

The early machines in the series (including the 2116) were direct-execution machines but the 2100 and later machines were microprogrammed. The 2100 offered a writeable control store allowing the user to extend and change the vertical microcode.

Descendents and variants

The Intel 8080 and thus even today's Pentium x86 and AMD x64 bear a slight resemblence to the HP-2100 as they also started out with a 16 bit AX and BX register, and it might not be a coincidence that Intel was just down the street from HP. History ironically shows that the most common IT and desktop computer architecture today, the x86 actually has more in common with the lowly HP 1000 than the stack-based HP 3000, a design with no explicit registers that is now extinct in modern processors.

The HP 9800 series desktop computer such as the HP 9830 also used this architecture, although they did not ultimately use any of the operating system or application software.

Instruction overview

• Arithmetic – Add, Increment, And, Or, Exclusive or
• Program Control – Skip, Jump, Jump to Subroutine
• Shift/Rotate – Arithmetic and Logical Shifts, 16- and 17-bit Rotates
• Optional – Multiply, Divide, 32-bit Load and Store, 32-bit Shifts

Model overview

Early models (1966-1969)

Core memory, hardwired CPU. Essentially a PDP-8 that has been pumped up to 16 bits and two accumulators.

• 2116A
• 2116B
• 2116C
• 2115A
• 2114A
• 2114B

Second generation (1970-1974)

Core memory, microprogrammed CPU. An option allowed user microprogramming.

• 2100A
• 2100S

21MX (1975-????)

Semiconductor memory, expandable to 1,048,576 words (one megaword).

• M-series – 2105A, 2108A, 2112A
• E-series – 2109A, 2113A
• F-series – 2111F, 2117F

They started out as refrigerator-sized rack computers that cost as much as a house with lights and switches on the front panels. The last models would use a 1 chip processor and fit under a desk using a console rather than front panel.

Operating System

The operating system shell even in the late 70s was very primitive, with a single-level file system. Running a FORTRAN compiler would look something like:

ru, f77, test&,test+,test%

meaning run the f77 program with source file, object, and exe. A modern unix command line uses an implied run, and files have dot extensions to distinguish between different file types for a given project. It may have been the most primitive of any competitive minicomputer at the time. The HP 1000 also was one of the few minicomputers that restricted names to only 5 characters, rather than the 6 common at the time, which made porting and even writing programs a challenge.

GRAPHICS/1000 was a FORTRAN 5 character name implementation of AGL, which was based on the HP 9830 graphics commands.

Introduction dates

According to the alt.folklore.computers Big List the early computers were introduced at the following times:

• Hewlett-Packard 2116A – Nov 1966
• HP 2115A – Nov 1967
• HP 2116A – Sep 1968
• HP 2114A – Oct 1968
• HP 2000A – Nov 1968
• HP 2114B – Nov 1969

(Note the conflicting entries for the 2116A, also the presence of the 2000A which is a time sharing system and not an actual computer as such.)

References

• Moffatt, Jeff (1999). HP 2100 Hardware Info.