Thursday, December 15, 2005

Retro Emulation

Is your office or basement full of old computers that you keep around just in case you "need" to use an old program or game that no longer runs on today's computers? Is your spouse threatening to throw you out if you don't get rid of all those old boxes in the attic or garage that contain your prized collection of old computers? Or maybe you just can't throw anything out and need a reason to sell all that stuff on eBay but still want to keep that favorite old software.

Well, you are not alone. Emulation software is the solution to your problems and is better than ever. For years, fans of early personal computers and video game technology have been faithfully creating emulation software that very accurately simulates real hardware. In this photo (click photo for larger view) I am running an Apple 1, Apple II, Sinclair ZX81, Atari 800, PC DOS, and a DEC PDP-11 running RSTS/E, all on my OS X MAC (I could have opened another shell and included UNIX on this list). These are running on the following emulators, in order; Pom 1 (Apple 1), OSX II (Apple II), NO$ZX8 running in DOSBox (Sinclair ZX81), Atari800MacX (Atari 800), DOSBox (PC DOS), and Simh running RSTS/E (DEC PDP-11).

These are just a few of the shareware or open source emulators that are out there, and a quick search on Google will turn up hundreds. You can also find many archives of old software (including on bittorrent) so that you may not have to go through the effort of converting your existing floppy disk based software to pc based emulator disk images. Now all you need to do is decide what to do with all that extra space around the house after you sell all that old equipment on eBay!

Tuesday, November 22, 2005

PDP Planet

What would a retro computing fan do if he or she had all the money in the world? Well, Paul Allen (billionaire and Microsoft co-founder) has created an organization, PDP Planet, and a project to restore one of his favorite vintage computers, the DEC PDP-10.

In fact, he has a whole collection of vintage DEC and other minicomputers. You see, in the early days of Microsoft, Paul and his buddy Bill Gates did all of their development work on minis, and despite the fact that the world is now dominated by Microsoft operating systems, they still have fond recollections of these old systems.

According to Paul, PDP Planet "fulfills my hope that the achievements of early computer engineers aren't lost to time. I wanted to provide a Web site and repository that recognized the efforts of those creative engineers who made some of the early breakthroughs in interactive computing that changed the world."

Check out the progress of his PDP-10 restoration, and get yourself an actual user ID on one of his personal PDP-10's running Tops-10. You can write and run your own programs from the internet on the actual vintage hardware. You'll be the hit of your next geek party when you show off your new program running on Paul's "personal computer"!

Tuesday, November 8, 2005

The First Killer App

The term "Killer App" is often used by technology marketing people to describe the next big application for a new technology, such as e-mail or the WWW being the Internet's killer app. When the first personal computers burst onto the scene in the late 1970's, there were no killer apps. In fact, there were few marketing people in this industry either. The field was dominated by hobbyists and techies, and practical applications were few, notwithstanding some teaching tools and games.

The Apple ][ was selling briskly to hobbyists and educators in 1978, but few yet saw the potential of the personal computer beyond this limited audience. Meanwhile, a Harvard Business School student named Dan Bricklin was working on a novel business tool idea and linked up with MIT graduate Bob Frankston to implement his idea on an Apple ][. When it was completed, they called it VisiCalc.

VisiCalc was the Killer App that transformed the Apple ][ (and Apple Computer Inc.) from a niche product to an essential business tool that virtually every company in America had to have. Today the spreadsheet remains ubiquitous in modern business, and virtually all of this can be traced back to this single invention created in an attic in a Boston suburb.

While VisiCalc, and the company created to sell this tool, Software Arts, are mere footnotes in computing history (Software Arts was later bought by Lotus which was eventually eclipsed by Microsoft), you can read about the creation of VisiCalc at Dan Bricklin's website, and even download an early version of VisiCalc for the IBM PC, which was made available to the public for free through an agreement by Lotus which still owns the copyright.

Today, over 25 years later, the personal computer industry is a several hundred billion dollar business. However, the creation of VisiCalc and the business revolution this started, long before the dominance of Microsoft, remains one of the most important events in personal computing history!

Thursday, September 29, 2005

Digital Archeology: Ancient UNIX

This is the first of a series of posts entitled Digital Archeology where I will be discussing interesting projects or amusing anecdotes involving the early days of computing. This story begins in 1969 in a small computer room at AT&T Bell Labs in Murray Hill New Jersey. Two ground breaking programmers have just created a new time-sharing operating system they have called UNIX. UNIX is unique in that the two developers, Ken Thompson and Dennis Ritchie, are describing this as the first "portable" operating system because they have written UNIX in a new language called C, invented by Ritchie himself. The minicomputer that this new operating system first came to life on was a DEC PDP-7.

Lets now travel 28 years forward in time to 2005 to see where I'm going with this. One of the best ways to experience what it was like for the early digital pioneers is to spend some time at the keyboard of one of these old machines. However, if you don't have the space to put three or four refrigerator size boxes in your living room or basement (the older DEC PDP models are still available on eBay if you have a moving van available for pickup), you can experience the next best thing through software emulation.

There are many software emulators that run on Windows or the Mac that create exact replicas of older original computer systems. The Apple I, Apple II, Sinclair ZX81, Atari 800, and some early DEC PDP models are some of my favorites. A simple google search for emulators will bring up hundreds of links for what is becomming a popular hobby for many vintage hackers like myself... more on this in another post.

The simh emulator (from the Computer History Simulation Project) is an open source effort that provides faithful emulation of many old computers including the PDP-11. If you were not aware, UNIX experienced its greatest growth in the 1970's and early 1980's on the PDP-11 with versions such as BSD (Berkley Systems Distribution). As a matter of fact, I got my first taste of UNIX on a PDP-11 in college.

Several dedicated enthusiasts have been sifting through tape archives and have resurrected a number of old disk images. These have been transfered to emulation software readable image files and are available on the web (see links on the simh site). Caldera has licensed several versions of old UNIX source code in the public domain.

I worked with UNIX V5 which I found fascinating in its simplicity as well as how little UNIX today has changed from this early version. The source code is till online in this version, as are sub directories titled "ken" and "dhr" containing early beta versions of several popular UNIX utilities, presumably left there in the early seventies by Thompson and Ritchie themselves!

Logging into this ancient system and navigating around the file system is a fascinating walk through time. The OS was small, yet still powerful. The UNIX source code includes original comments, and anyone with an interest in the origin of both the C language or UNIX itself will find this an absorbing journey into the past.

Tuesday, February 15, 2005


Looking for something to put on your coffee table that really captures the essence of that vintage computer collection of yours? How about a beautiful book on photo grade stock with pictures of all your favorite personal computers from the seventies and eighties and more? Check out this book by Gordon Land called DIGITAL RETRO the evolution and design of the personal computer. All of my favorites are in here; Apple I, Apple II, Sinclair ZX81, Atari 800, IBM PC, IBM PCAT, Macintosh and over 40 others. Great photos and short historical descriptions accompany each making this an interesting read from end to end, or just fun to browse.

An reviewer writes of this book "Take a visual stroll through the early days of personal computing, from 1975's seminal MITS Altair to 1988's failed NeXT cube, before the market bifurcated between Mac and Windows users. This 192-page paperback examines 40 classic computers of yesteryear, each depicted from all sides with full-color photography and annotated with original specifications and pricing. Laing's text also reveals many juicy tidbits about the companies and personalities that dominated the industry in its infancy."

Thursday, January 27, 2005

The Sinclair ZX81

The year was 1981. IBM had just announced the IBM PC for the modest sum of $3,000. The Apple II was everywhere. I had been programming various computers ranging from DEC PDP-11's to Apple II's and the dream of owning my own computer was still out of reach for this college physics student and electronics hobbyist.

Then came the Sinclair ZX81. Here was a kit, advertised in BYTE magazine, that you could build and own for $99! It didn't look like much more than a large calculator, but to someone with my desire to soak up every bit of knowledge about computers that I could find, this was my ticket to a whole world of possibilities.

It was ordered, arrived, and I quickly put my soldering skills to use. In two days I was programming Sinclair BASIC and reading a Sinclair users group newsletter out of Harvard describing undocumented tricks that would allow you to load a Z80 machine language program into memory and call directly to your code, bypassing the BASIC interpreter and making the Sinclair architecture as accessible as any minicomputer or personal computer at the time.

I was soon writing machine language on a yellow pad and hand assembling into hexadecimal bytecodes which I would write in the left column of the paper. I think I still have some of those program listings somewhere. While hand coding this way was extremely tedious, the feeling of euphoria when finally seeing your debugged program working was just reward.

If I were asked to describe the biggest weakness of the Sinclair ZX81, it would have to be the storage... audio cassette tapes, that is. It took a lot of messing around with the volume control on my tape recorder. It was easy to lose a program, and they were stored sequentially so you had to play through to the point in the tape you were interested in. You got very accustomed to listening to these tapes as you were rewinding or fast forwarding to the program you were looking for, and you could often recognize a piece of code by how the beginning sounded.

And of course there was the constant threat of the "wiggle" crash. This invariably occurred after you just spent an hour painstakingly typing in a large program listing on the membrane keyboard, pressing hard on the no-feedback keys when the computer moved slightly and the external rampack (seen in the ad above) would wiggle ever so slightly, and cause the system to crash losing all that hard work. I suppose many ZX81's were thrown out a window for just that reason!

To many, the Sinclair ZX81 was a toy. To me, it was a development system. Here is a picture of a buffered expansion board from Computer Continuum Inc., with the ZX81 mounted on edge. In the buffered slots are some of my wire wrapped expansion cards that I built for various college physics projects. The first is a UART serial interface, the second card is a 2K memory expansion, and the third is a 8255 PPI interface. I was planning to add a real keyboard and mount this in a box for a home control application... another unfinished project.

The ZX81 still has a strong following today 23 years later! There are a number of emulators out there and many web sites with code to download. comp.sys.sinclair is a good place to see what the latest news is on new versions of emulators or code. You can even still buy new unbuilt ZX81 kits. Zebra Systems has several hundred kits available for the original price of $99 so that you can still experience the thrill of building one of the earliest (and least expensive) personal computers from the 80's!