Old Vintage Computing Research

I've mentioned on the blog several times the continuum that exists between handheld computers and pocket computers, battery powered devices in rather small form factors that are nevertheless fully-fledged general purpose computers -- arguably more so than the modern locked-down smartphone has become. Some of these diminutive systems are best considered "handhelds," with larger size, larger keyboards, more power and (often) less battery life, and some are definitely "pocket computers," with smaller size, smaller keys, less power and (usually) better battery life. For example, systems like the Tandy PC-4/Casio PB-100 or Tandy PC-3/Sharp PC-1250 would be considered "definitely a pocket computer," while the Epson HX-20 or Kyotronic 85 systems like the NEC PC-8201A or TRS-80 Model 100 would be considered "definitely a handheld computer," and you can probably think up some examples in between.

Well, here's a notable example of one single architecture that birthed both types of machine, and it came from a company not really noted for either one: Texas Instruments.

TI certainly made calculators and many of those were programmable by some means, but neither handheld computers nor pocket computers had categorically been in their repertoire to date. Nevertheless, here we have the 1983 Compact Computer 40 -- using the AA battery for scale, at that size definitely a handheld -- and above it the 1985 TI-74 BASICALC, notionally a "BASIC programmable calculator," but actually an evolved version of nearly the same hardware in less than half the size. Thanks to the ingenuity of the Hexbus interface, which due to TI's shortsightedness was never effectively exploited during that era, we can get a serial port running on both of these with hobbyist hardware. If we have a serial port, that means we can bring up a terminal program -- which we'll write from scratch in assembly language for shell and Gopherspace access.

But how would a Unix shell work on a single line screen, or for that matter, a Gopher menu? We'll explore some concepts, but before we do that, for context and understanding of their capabilities we'll start with the history of these machines -- and because their development is unavoidably tangled with TI's other consumer products and their home computer family, we'll necessarily rehash some of those highlights and nadirs as well.

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Way back (well, six months ago, anyway), when I was wiring up a Gremlin Blasto arcade board, we talked at length about this 1978 arcade game's history and its sole official home computer port by Milton Bradley to the Texas Instruments 99/4A. In the single player mode you run around in a maze and try to blow up all the mines, which can set off sometimes impressive chain reactions, all the while making sure you yourself don't go up in flames in the process. The TI-99/4A version was the Blasto I originally remember playing as I never did play Blasto in the arcades. (Also, for the record, we're not talking about Sony's unrelated Blasto for the PlayStation which, other than having the voice talents of the late and lamented Phil Hartman, was apparently a traumatic slog both for its developers and the few people who actually played it.) To the credit of its three composite authors, it is a competent and accurate conversion that also adds configurable options, colour graphics and music; in fact, TI's Blasto is probably my favourite game on the /4A, more so than any other cartridge. On the other hand, because it's an accurate conversion, it also inherits all of the original's weaknesses, which admittedly hail from the limited CPU and ROM capacity of the arcade hardware.

So, in that article, I mentioned two future Blasto projects. One is to save my pennies for a custom arcade cabinet to put the board in, though I just spent a cool grand plus on tires which used up a lot of those pennies and I've also got Christmas presents to buy. But the second was to write my own take on TI Blasto and soup it up. This project is the second one from my bucket list that I've completed. It took a couple years of work on it off and on, but it's finally done, with faster action and animation, a massive number of procedurally generated screens, and fully configurable gameplay.

I've christened it Oblast, and it's free to play on your real Commodore 64 or emulator. Let's talk about what's the same and what's different.

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Because my sisters were taking rollerskating lessons and my own rink skills mostly consisted of pratfalling, my mother would occasionally give me quarters for the arcade instead. This was my first introduction to pinball -- one of these days I'll have room for my first pin, a Williams Pin-Bot, alongside my Sopranos and ST:TNG machines -- and quite a few arcade video games that I later got to play on my Tomy Tutor, Commodore 64 and Intellivision at home.

However, a few games I played on the Tutor first before I ever played them on an arcade cabinet (Pooyan and Loco-Motion come to mind), and one outlier I never played in the arcade at all. Earlier, when we briefly lived in the Antelope Valley north of Los Angeles, the first computer I got to ever touch (albeit briefly) was a Texas Instruments 99/4A in the third grade classroom. Among other cartridges it had a brisk and zippy arcade conversion called Blasto from Milton Bradley which never got ported to any other system, and it wasn't until after college that I reacquainted myself with the TI version in emulation. I never actually got to put quarters in one.

A shame, because by then we lived on the mean streets of east county San Diego, California -- not far, it turns out, from the corporate office of Gremlin Industries where the original arcade incarnation of Blasto was developed (completely unrelated to the later PlayStation game). I spent most of my childhood and got my bachelor's degree in San Diego, and I still consider it my hometown. Decades later I managed to pick up an original service manual for yuks last year, which sat mostly pristine in my collection, but much more recently an actual Blasto logic board based on an 8080A CPU turned up on eBay. After waiting awhile for the seller to cut the crap, they finally posted it at a not totally unreasonable price for a completely untested item, as-was, no returns, with no power supply, no wiring harness and no auxiliary daughterboards. At the end of this article, we'll have it fully playable and wired up to a standard ATX power supply, a composite monitor and off-the-shelf Atari joysticks, and because this board was used for other related games from that era, the process should work with only minor changes on other contemporary Gremlin arcade classics like Blockade, Hustle and Comotion [sic]. It's time for a Refurb Weekend.

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We got it in 1983, I think, so it only took me about 41 years to get around to it. This Tomy Tutor isn't a replacement system I secondarily acquired, nor is it a Ship of Theseus Frankenstein rebuild. This is my actual first computer, in its original case, on its original components, with the Federated Group sticker still on the original box. And it still works. Now, why so long? Well, for one thing, it was only supposed to be a training wheels computer because a full Commodore 64 system would have cost too much, but my folks wanted to see whether we'd take to a home computer and His High Holy Munificence Fred R. Rated was blowing these babies out for a song by then. The receipt has long since disappeared, though $99 sounds about right plus maybe around $40 or so for a joystick, cassette deck and some cartridges, compared to somewhere between $200 and $300 for the recently discounted 64 -- which didn't include anything else. (It tells you something about our family finances at the time when a C64 was too expensive.) I immediately started writing my own BASIC programs on it in its perverse little BASIC dialect and when my folks indeed saved up and bought us a C64 system the next year (complete with 1702 monitor and 1541 disk drive), I refused to use it. In retaliation my best interests, my parents forcibly relocated the Tomy to storage and I went on to do even bigger things on the Commodore, making it, not the Tutor, the defining computer of my childhood. That's why there's still a Commodore 128DCR on my desk.

The other reason is that there was never really a simple way to do it. Even when I found out what CPU was actually inside (incredibly a 16-bit TMS 9995, an evolved version of the TMS 9900 in the Texas Instruments 99/4 and 99/4A), there was never a Tomy assembler, and other than its small amount of scratchpad RAM (256 bytes) the entirety of the Tutor's 16K of memory is tied up in the 9918ANL VDP video chip. That sort of architecture was typical for the family, but that also means that almost everything is stored in non-executable VDP RAM, so short of burning your own cartridge EPROMs there's no way to actually create and run a machine language program on the Tutor. The first flashcart for the Tutor didn't exist until around 2016 and it was still all ROM; furthermore, while the 99/4A could have its CPU-addressable RAM expanded (as well as the 99/8, its unreleased successor to which the Tomy Tutor is closely related), there wasn't ever a Tutor RAM expansion cartridge either until very recently. But now there are multiple homebrew options even for obscure home computers like this one, and at last I've got my own assembly language program finally running on it.

And it's all done with its own, better I/O routines (if I do say my own better self) as a basis for bigger projects. But first, a little tour of the Tutor itself, and then we'll dig in.

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When my parents sold the house and moved to the great white north, they dropped off a few boxes of my stuff that was still in the garage. Now that we're getting things cleared away in case we have to make a move of our own in the not-so-distant future, it was time to go through those boxes, and one of the boxes was this, my old Mattel Electronics DUNGEONS & DRAGONS(tm) Computer Labyrinth Game.

This is the bigger, more deluxe of the two Mattel dedicated D&D games (the Intellivision of course had its own set, and we had a Tandyvision ourselves), the other being the DUNGEONS & DRAGONS(tm) Computer Fantasy Game. That was a handheld unit with a surprisingly compelling implementation of Hunt the Wumpus, and something we might talk about another time. This one is more like a board game, but with a computer antagonist and audio.

The box says copyright 1980 but I think we got it late 1982 or early 1983. Either way, I was probably too young for this game at the time: it advertises 8 and up, and I would have been around six or so. It requires you to juggle a number of different audio signals and build up the maze and the objects in it (you, your competitor, the dragon, the treasure, your lifeless defiled corpses when you try to get the treasure, etc.). My recollection is that we barely played it at all.

Well, better late than never. And hey: let's find out what makes it tick. (Teaser: it's four bits and we have an annotated die photo. Read on.)

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It seems like everything has flash. Flash mobs, flash photography, Flash Gordon, flash memory. (Other than the past couple years, of course, which haven't been very flash.) And, because solid-state-all-the-things, you can get flash storage devices for tons of classic computers where even the tiny microcontroller in the SD cards is probably more powerful than the systems they're being interfaced to. Why, you can even connect one to an MOS KIM-1, the famous mid-1970s MOS 6502 single-board computer. Now at last you don't need to rekey everything in or screw around with an audio recorder.

But, of course, if you've read this blog for any period of time you know I don't go in for that sort of new-fangled nonsense around here. I like my retrocomputing frivolities period-correct. What the KIM-1 really needs as a mass storage medium ... is bubble memory.

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The first terminal I ever used was a teletype. Somehow my buddy when we were in high school got a hold of this weird "printer typewriter" which was none other than one of the famous Texas Instruments Silent 700 series.

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