Retrochallenge 2017/04:
Personal Computer Space Transactor 2001

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Mockup of the title screen

A mockup of the title screen …
If this ain't the 70s from space … Already totally worth it! ;-)

About this Project

As it happens, the Commodore PET 2001 is 40 this year (announced in January 1977 at the Winter CES, first units delivered in October). And, as it happens, I've a new toy. Sadly, it's not a PET (I don't even have a Cat), but the next best thing, Thomas Skibo's PET 2001 emulator. And, as it's written in JavaScript and changes and redistribution are permitted, I'm keeping playing around with it. Morever, I've been musing about some of the most classic video games lately, and while doing so, there was always this strange while tempting idea about doing some on the (virtual) PET.

Last time, we did a Computer Space simulator for a rather exclusive piece of hardware (one unit operational in total), this time, we'll redeem ourselves from any accusations of elitism by something more popular. But it won't be just a simple simulator, no, it'll be a Personal Computer Space Transactor (if you don't know what this would be, it's pretty much the same as a simulator, but using an even more inappropriate display technology).

Speaking of display technology, the PET (at least as delivered by Commodore) has no graphics mode, but just a 40 × 25 character display. And it's not in ASCII, but in PETSCII, including some weird character code assignments and an assortment of block graphics symbols. And, if this weren't strange enough, there's also a special encoding used by the video hardware, known as screen characters. However, there isn't much to write home about, as this all well known, because of the most popular computer of all times and PET's successor, the Commodore 64 (which had, of course, graphics modes and sprite graphics as well, features completely lacking on the PET). Anyway, it's always fun to play around with character graphics and even producing just a mockup by typing some patterns onto the screen is already strangely rewarding. As for our project, the real challenge will be to produce anything reminding of an arcade game with the limited resources of the graphics hardware, in order to put something onto the screen, which had been already retro when the first PETs were delivered.

Mockup of Computer Space 2001 running on an original PET 2001 computer

"Artist's impression" of what we're intending to do …
(Image of Commodore PET 2001: © 2013; edited, N.L., 2017.)

Hardwarewise, the PET features a 6502 processor running at the standard 1 MHz — and we'll do this little project properly, in machine language. The operating system hasn't changed much for the 8-bit Commodore machines that were to follow the PET (the VIC 20, the C64, etc), so most of the stuff we'll need to know isn't much of a secret either. I've not decided on the tools yet, maybe we'll extend the emulation by a full web-based IDE in the process. Let's see.

P.S.: If you happen to be interested in the real thing, don't miss the project by Frank Linde, who is going to be playing around with the original PET hardware and rather advanced graphics from the future (think VGA).

The Episodes

— finis —

— This series is part of Retrochallenge 2017/04. —