Reverse-engineering Roadsearch Plus, or, roadgeeking with an 8-bit CPU

Sorry, Doc Brown: we still needed roads in 1985. That meant paper atlases and misfolded roadmaps and a lot of stereotypical male anxiety asking for directions. Fortunately, in 1985, this problem also had a solution.

Yes, if your car inverter could handle a 45-ish watt load — and your wife doesn't want her seat back right away — you could navigate major routes across America on your home computer like this portable Commodore SX-64. I particularly enjoyed writing this article because my other irredeemably nerdy habit is roadgeeking, exploring and mapping highways both old and new, and it turns out that 8-bit roadgeeking on ordinary home computers was absolutely possible.

For computers of this class, devising an optimal highway route becomes an exercise not only in how to encode sufficient map data to a floppy disk, but also performing efficient graph traversal with limited hardware. Today we'll explore Roadsearch-Plus, one of the (if not the) earliest such software — primarily on the Commodore 64, but originating on the Apple II — and at the end "drive" all the way from southern California to British Columbia along US Highway 395, my first long haul expedition, but as it was in 1985. Buckle up while we crack the program's runtime library, extract its database, and (working code included) dive deeply into the quickest ways to go from A to B using a contemporary home computer.

A real PowerBook: the Macintosh Application Environment on a PA-RISC laptop

I like the Power ISA very much, but there's nothing architecturally obvious to say that the next natural step from the Motorola 68000 family must be to PowerPC. For example, the Palm OS moved from the DragonBall to ARM, and it's not necessarily a well-known fact that the successor to Commodore's 68K Amigas was intended to be based on PA-RISC, Hewlett-Packard's "Precision Architecture" processor family. (That was the Hombre chipset, and prototype chips existed prior to Commodore's demise in 1994, though controversy swirled regarding backwards compatibility.) Sure, Apple and Motorola were two-thirds of the AIM alliance, and there were several PowerPC PowerBooks available when the fall of 1997 rolled around. But what if the next PowerBooks had been based on PA-RISC instead?

Well, no need to strain yourself imagining it. Here's nearly as close as you're gonna get.

In October 1997 you could have bought a PowerBook 3400c running up to a 240MHz PowerPC 603e for $6500 [about $13,000 in 2025 dollars], which was briefly billed as the world's fastest laptop, or you could have bought this monster new to the market, the RDI PrecisionBook running up to a 160MHz (later 180MHz) PA-7300LC starting at $12,000 [$24,000]. Both provided onboard Ethernet, SCSI and CardBus PCMCIA slots. On the other hand, while the 3400c had an internal media bay for either a floppy or CD-ROM, both external options on the PrecisionBook, the PrecisionBook gave you a 1024x768 LCD (versus 800x600 on the 3400c), a bigger keyboard, at least two 2.5" hard disk bays and up to 512MB of RAM (versus 144MB) — and HP-UX.

And, through the magic of Apple's official Macintosh Application Environment, you could do anything on it an HP PA-RISC workstation could do and run 68K Mac software on it at the same time. Look at the photograph and see: on our 160MHz unit we've got HP-UX 11.00 CDE running simultaneously with a full Macintosh System 7.5.3 desktop. Yes, only a real Power Mac could run PowerPC software back then, but 68K software was still plentiful and functional. Might this have been a viable option to have your expensive cake and eat it too? We'll find out and run some real apps on it (including that game we must all try running), analyze its performance and technical underpinnings, and uncover an unusual artifact of its history hidden in the executable.

(A shout-out to Paul Weissman, the author and maintainer of the incomparable PA-RISC resource OpenPA.net, who provided helpful insights for this article.)