Hewlett-Packard
HP-11c

Sharp PC1245
pocket computer

NEC PC8201a
laptop computer

EO tablet

Yarvik TAB250

Apple iPhone 5G clone



Other electronic gadgets
Battery Manager Ultra
Samsung ML-1640 laser printer
NBOX Media Player
LED-2 Inexpensive Video Projector


Also see:
Cycling Holidays
DutchBikeBits.com


NEC PC8201a Laptop Computer

The NEC PC8201a was my first laptop computer. These machines were produced by Kyocera for several companies and branded by more well known names. The Tandy Model 100 is perhaps the most well known version, but there were also versions sold as Kyocera and Olivetti products as well as my NEC. Produced in 1983, my machine has a whole 16 Kb of RAM internally, an 80C85 8 bit processor running at 2.5 MHz and connectivity through serial and parallel ports.

The screen offers a resolution of 240 x 64 pixels, or 40 x 8 characters. Not much. This is much less than any more modern portable device, but the NEC still wins over most portable computers of any time for the quality of its keyboard. This is a machine for typing on, and producing content, not for consuming content.

The PC8201a is a very robust computer. Even now, nearly 30 years after production, it still works perfectly. The larger capacity modern rechargeable AA cells means that four of these will keep it running for weeks. Astonishing battery life compared with modern devices.

Usage

I worked as a software engineer for 20 years, stopping at the end of 2003. Most of my work had been in C and C++ or in Assembler. While I never wrote programs for the NEC, save for small amounts of BASIC for house-keeping functions or to work out sums, I used it a lot to write code for other machines. Being able to work on the go was quite novel, and much of my software development when I was contracting in the 1980s was done in a quiet spot a bicycle ride's distance from home.

The NEC never lost any of my work due to battery problems, or any other problem.

Internal view


The main printed circuit board. Everything is through-hole mounted.


The underside of the keyboard and display. The display printed circuit board is of another generation, with surface mounted components. Note that half of the surface mounted chips are mounted upside down in cut-outs in the board. This is more expensive than mounting right-way-up so must have been necessary to make routing easier on the PCB.

The HD44102 display controllers each contain 1600 bits of RAM. In this application they each have to control 1536 bits of display so the RAM is nearly entirely used.


The beating heart of the computer is an OKI second sourced version of the Intel 8085 processor. This example is an 80C85A, the CMOS version which has about an eighth of the power consumption of the original NMOS 8085A.


There is 16 Kbytes of RAM in the computer, on two memory modules. Each module contains four Toshiba TC5518 2 Kbyte RAM chips (two on the top, two on the bottom).


On the bottom of the case there's a removeable panel for expansion. The socket on the left contains a masked ROM of the operating system and Microsoft BASIC. This is rumoured to contain the last production code written by Bill Gates himself. So far as I've been able to tell it's very good code. No bugs and good speed given the restrictions of the system.

The first socket position, ROM 1, is for extra code. It was once possible to buy a spreadsheet, for instance, which could be installed here. The RAM sockets are not for standard RAM chips. They're slightly wider than usual and intended for modules containing the TC5518 chips as found inside the computer.

Leaking battery

Like many other devices, the NEC PC8201a contains a backup battery to preserve memory contents when the main battery is disconnected. This still operated correctly in my laptop as late as 2014, but it was showing some signs of starting to leak.

Leaking Nickel Cadmium batteries can damage printed circuit boards so I decided to replace the device.

My replacement consists of two 5 V 0.05 F memory backup capacitors in parallel for a total of 0.1 F, soldered into the original position of the battery on the main printed circuit board.

The exact value of these capacitors doesn't matter much. I used these two in parallel because I had them to hand and because two of these capacitors fitted easily in this location.

The replacement memory capacitors can never leak, ensuring my NEC remains in operating condition well into the future. I plan to start using the machine again because its keyboard is superior to any other laptop that I've owned and it boots far faster than any other laptop that I've owned.

Accessories

I also have the matching NEC PC8281A cassette deck ("mass storage") and an expansion cartridge for an additional 32 K of RAM.

For some years I've been meaning to make my own additional 32 K of RAM as an internal option. However, while the parts have been floating around for some years, I've still not done this. You can find instructions here.

What can you use this for ?

When I first owned this computer I worked from home. This computer gave me freedom. If I'd had enough of the four walls surrounding me, I could cycle to the local beach and write code or documentation just as efficiently there as I could have when sitting at home. Obviously 32 K of RAM doesn't go all that far, so I'd take relatively short excursions.

In the late 1980s / early 1990s I worked as a computer consultant (mostly designing solutions for customers which I could write in C and various assemblers) and travelled around Britain to visit customers. I'd sometimes work at an address for weeks or months at a time. This computer, its accompanying tape deck to save documents, a dot matrix printer to print them on would go with me as my mobile office. With this combination, I could continue to communicate with clients or family and even write a little code for other projects.

I also took a really high quality portable tape deck and some nice powered speakers for entertainment.

You'll note that I didn't take a modem with me. At that time, it wouldn't have helped much. I had internet access, but not yet "officially".

Other sources of information

Perhaps the most useful source of information about the NEC PC8201a is the excellent WEB8201 website.

These days I sell bicycle components and lead cycle tours for a living.