Hewlett-Packard Model 85
Introduced:December, 1979
Released:January, 1980
Weight:20 lbs
CPU:custom HP 8bit @ 0.613MHz
RAM:8K, 64K max.
Display:built-in 5 inch monitor
32 x 16 text
256 X 192 graphics
built-in 32 char. thermal printer
Storagebuilt-in DC100 217K tape drive
Ports:four expansion ports

Similar in appearance to the IBM 5100 from five years earlier in 1975, the Hewlett-Packard HP-85 is an all-in-one portable computer system with a built-in keyboard, 5" screen, thermal printer, tape storage unit, and the BASIC programming language.

With its top off, it can be seen that the HP-85 has a clean and simple layout.

On the left is the monitor and display circuitry, on the right is the thermal printer and tape storage mechanism.

The main motherboard is beneath the keyboard, shown here folded up. Except for the eight memory chips, all of the chips are custom HP designed.

There are four ports on the back for expansion carts.

The HP-85 has a custom Central Processor (CPU) from Hewlett-Packard which runs at a slow 613KHz. Why? HP says:
Why does HP use its own custom CPU? One of the most important reasons is ACCURACY. Where other computers do binary arithmetic, the HP-85 does its arithmetic in BCD (binary coded decimal). Our calculators do BCD arithmetic, and we've spent years testing and perfecting those algorithms, so we KNOW that the answers returned by the HP-85 are accurate to 12 digits. Real number calculations in the hp-85 are performed internally to 15 significant decimal digits and rounded to 12 digits for presentation.

There are a couple of ways to build a CPU - make it simple and run it fast, or make it complex and run it slow. Most manufacturers try to drive their CPU's as fast as possible. Four megahertz is typical - the speed is limited by the physical characteristics of the device, like capacitance. We have followed the second strategy, performing many operations during each clock cycle. The clock speed is 613 kilohertz!

But, execution speed is more than just a function of hardware design, and the HP-85 executes programs on the same order of time or faster than other personal computers on the market. In concert with the design of the hardware, the firmware design equally effects the speed of the system.

But all of this is another story. The point is that the HP-85 is a machine that is inherently accurate, fast, and affordable. You might argue, though, that there is a penalty for using our own custom CPU, that software written in machine language for the more common varieties of CPU's must be rewritten to run on the HP-85. And the task of translating these assembly level programs is not straightforward; the HP-85 relies on its unique architecture for its speed. Anything written for a Z-80, for example, translated straight across, would utilize only a small fraction of the CPU's power.

But really, incompatible software is a short-term problem. Most forthcoming software will necessarily have to written in high-level language, making it independent of the actual processor used. The reason is due to increasing software costs and the desire to implement more complex programs. No one will be able to afford to develop important new applications in machine language, especially since it will be unnecessary. Because of the increased capabilities of future-generation microprocessors, coding efficiency won't really matter. Stretch it to the limit and you'll see what I mean - perhaps by the year 1999 all the software ever written will run in less than a minute. But you don't have to wait until then; forward thinking software houses have already shifted gears.

Released in 1982, the low-profile HP-86 personal computer offered users more options and expandability than the HP-85, which had been introduced two years earlier. It has no internal display, printer, or data storage - all of these are now external peripherals. The HP-86 came standard with 48K of RAM.

In 1982, Hewlett-Packard released the HP-87 computer, as seen here to the right.

It sacrificed the built-in printer and tape backup for the extra-wide video screen. The HP-87 is capable of displaying 80 columns X 16 rows of text, as well as 400 X 240-dot graphics, on a unique high resolution 9" X 5" display.

The HP-87 has 32K internal RAM - four times that of the HP-85. The HP-87XM has a whopping 128K RAM.

Related Links

  • HP-85 from hp.com
  • HP-85 cartridge information
  • HP-85 from R/S Programmable Calculators
  • HP series 80 database from Cyberspace Outpost of Eric Bal
  • HP Museum
  • Hewlett Packard 85 Programmable Calculator/Computer from The Old Calculator Web Museum
  • HP-85 from voidware.com - includes how to fix your gummy-wheel!
  • www.series80.org - HP Series 80 Web Site

  • History of Hewlett-Packard Computers

    • 1972: Hewlett-Packard pioneers the era of personal computing with the first scientific hand-held calculator, the HP-35, which makes the engineer's slide rule obsolete.
    • 1973: Stephen Wozniak joins HP.
    • 1976: Steve Wozniak proposes that HP create a personal computer. He is rejected.
    • 1976: October - Steve Wozniak remains at HP, but is soon convinced that he should leave and join Apple Computer.
    • 1976: HP begins Project Capricorn, to build a computer-like calculator.
    • 1980: January - HP completes work on the Capricorn project, producing the HP-85. With a 32-character wide CRT display, small built-in printer, cassette tape recorder, and keyboard, it sold for US$3250.
    • 1980: February - HP announces that it will switch to Japanese makers of 16K RAM chips. HP had examined chips from Japan and the US, and found that chips from the best American firm had six times the failure rate of the worst Japanese producer.
    • 1982: HP introduces the HP-75C portable computer. Price is US$995.
    • 1983: June - HP introduces the HP-7475A 6-pen plotter, for US$1895.
    • 1983: October - HP unveils the HP 150 microcomputer.
    • 1984: May - HP introduces the HP 110 laptop computer.
    • 1984: HP introduces the LaserJet laser printer, featuring 300dpi resolution, for US$3,600
    • 1987: HP releases the HP PaintJet color inkjet printer
    • 1989: May - HP buys workstation maker Apollo Computer for US$476 million.
      Source: Chronology of Events in the History of Microcomputers

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