HP 2100

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The HP 2100 was a series of minicomputers produced by Hewlett-Packard's from the mid 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 mid 1960s. It was designed by HP's Dymec division, after absorbing Data Systems Inc. (DSI), a subsidiary of Union Carbide. DSI had designs for a 16-bit minicomputer called the DSI-1000, which would eventually evolve into the 2116A through HP's involvement.

The 2116A is a 16-bit word-addressed general purpose computer. Main memory is 4096 words (4K), expandable to 8K of magnetic core in mainframe, or 16K with a memory extender. The 2116A features 16 I/O slots in mainframe, a 10 Mhz clock and a memory cycle time of 1.6 microseconds. The 2116A had two subsequent revisions: the 2116B added support for up to 32K with a memory extender, and the 2116C incorporated a more compact model of core memory, allowing the full 32K to be housed within the computer mainframe.

In 1967, HP introduced the short-lived 2115A, a cost-reduced variant of the 2116A with only 8 I/O slots, a bulky external power supply, and a 2116-style front panel. In 1968, the 2114A was released as a further cost-reduced variant, stripped of such options as DMA and extended arithmetic. The 2114A featured a redesigned front panel, with reduced register displays and illuminated proximity-sense switches. The 2114 saw two further revisions: the 2114B added single-channel DMA and HSIO options at the expense of a single I/O slot, and 2114C supported up to 16K maximum core in mainframe, at the expense of yet another I/O slot. The 2115A and 2114A/B/C have an 8 MHz clock and a 2.0 µs cycle time.

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[edit] 2100 series architecture

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.

[edit] Descendants and variants

The HP 9810, 9820 and 9830 desktop computers used a slow, serialized TTL version of the 2116 CPU, although they did not ultimately use any of the operating system or application software. In 1975, HP introduced the BPC, the world's first 16-bit microprocessor, using HP's NMOS-II process. The BPC was usually but not always packaged in a ceramic hybrid module with the EMC and IOC chips, which added exended math and I/O instructions. The hybrid was developed as the heart of the new 9825 desktop computer. The later 9845 workstation added an MMU chip.

The major differences between the original 2116 architecture and the BPC microprocessor are a completely redesigned I/O structure, and the removal of the ability to execute multiple levels of indirect addressing. The elimination of multiple indirection made an extra bit available in the memory reference instructions, allowing the maximum memory capacity to be increased from 32K to 64K. The BPC also added an input allowing the "current page" to be PC-relative, rather than a power-of-two aligned page.

The BPC was used in a wide range of HP computers, peripherals, and test equipment, until it was discontinued in the late 1980's.

The HP 2100 is one of many 8 and 16 bit machine architectures said to be inspired by the PDP-8, These can be characterized by a small number of accumulators (such as A and B) rather than a relatively large number of regular registers (such as R0-R7 or R15) found on the PDP-11.

[edit] 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

[edit] Model overview

[edit] Early models (1966-1970)

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

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

[edit] Second generation (1970-1974)

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

  • 2100A
  • 2100S

[edit] 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.

[edit] Operating systems

The operating system shell even in the late 70s was very primitive, with a single-level file system. The command to run 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. Newer RTE-A operating system for HP 1000 provided conventional directory structure with 16.4 file names.

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

Alternatively, a specific dual-processor configuration was sold that could run HP Time-Sharing BASIC. In this system, a well-equipped 2116 acted as the main processor while a 2114 acted as the communications multiplexor, simulating many UART channels in software. Later, 2100-series processors were substituted.

[edit] Introduction dates

  • HP 2116A – Nov 1966
  • HP 2115A – Nov 1967
  • HP 2116B – Sep 1968
  • HP 2114A – Oct 1968
  • HP 2000A – Nov 1968 (2116-based timesharing system)
  • HP 2114B – Nov 1969
  • HP 2116C – Oct 1970
  • HP 2114C – Oct 1970

[edit] References

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