(2025-04-07) Old, offline, outstanding
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It seems that I keep getting some items with interesting history even to this
day. For instance, two days ago, I was given my real father's mechanical 
pocket watch on a chain as a birthday present. Of course it works but is 
hellishly fast and does need some maintenance since it was never given one 
since 1990 or something like that when it had been bought, however, that's 
not what I'm here to talk about today. There is yet another artifact that I 
purchased last week, and I bet that, just like with that custom-engraved 
Seiko SBTM091 I already wrote about, the sellers didn't really know what 
they were selling. They were selling it as a "programmable calculator with 
formula entry capabilities", sic. Meanwhile, it even says "HANDHELD COMPUTER 
/ ORDINATEUR PORTABLE" on the backplate, and this is what this Texas 
Instruments TI-74S really is.

To be honest, I don't even know where to start. I remember dreaming about
such a device since like 2001 or 2002, when I was a schoolboy and was given 
my first programmable calculator, MK-52, that ate batteries away so quickly 
that it was impractical even trying to take it to school with no power 
outlets available. On a positive side, one of my classmates had an MK-61 
(almost the same internally) so we got another topic to chat about. The 
school library even had a couple of books about Soviet programmable 
calculators, and the librarian let me keep them for several years straight 
as no one else was interested in this topic. In one of those books, I 
remember reading about MK-85 (that, as I found out many years later, was 
visually a Casio FX-700P clone but built on a PDP-11-like architecture) that 
could do BASIC which might be more interesting for me than just plain RPN 
keystroke programming and it still was available from some second-hand 
sources at the time, and I even asked my parents about it, but they had a 
hard time understanding what I was asking about and then said "no, study 
well and we'll get you a REAL computer". Oh well, they did get a standard 
budget PC in 2004 but it wasn't portable and, of course, they got it more 
for themselves than for me. Yes, it was that PC that I later learned C and 
JS programming on, but it was MK-52 that taught me byte-to-byte optimization 
and the basics of the stack and indirect calling even before that. When I 
got my first cellphone, Nokia 3100, in 2005, I even managed to install 
Mobile BASIC there, but the documentation was non-existent and the programs 
were too inconvenient to type in. Later in life, I got a laptop, a 
smartphone, a lot of other things, but a small QWERTY machine with a full 
programming environment onboard remained an unobtainium for me for many 
years to come.

As the saying goes, "if you had no bike in the childhood but got a Bentley as
an adult, you still had no bike in the childhood". So, over a week ago, out 
of boredom, I just typed in "programmable calculator" on a local online 
marketplace website to see if anything new would come up in the search 
results compared to what was there half a year ago. To my surprise, there 
was exactly one new result, and it was this TI-74S. Of course I didn't 
hesitate to place an order as the lot turned out to be more than affordable 
(less than 30 USD for such a treasure). The device came in a stock hard case 
and, while the case has been scratched pretty badly, it served its purpose: 
the computer's condition itself is near mint. And it even came with a flash 
ROM cartridge tailored for a German insurance company VGH with preprogrammed 
life and estate insurance cost calculations for the year 1995. Which in 
itself is an interesting thing since the S variant was manufactured from 
1986 to 1992 (my particular item was made in February 1988), which means 
Texas Instruments themselves kept offering post-production support for 
various companies long after the model had been discontinued. Also, despite 
the TI-74's character table has German umlauts near the end of it (along 
with some Greek characters and even katakana), the insurance cartridge 
software, displaying messages solely in German, didn't use those umlauts and 
substituted them with ae/oe/ue respectively. Maybe the cartridge developers 
didn't even realize that those characters were actually accessible, who 
knows.

So, what exactly is TI-74S? After reading through some sources, I can say
that this is the last of the last in the TI-99 line of computers. It all 
started with refactoring an Altair-like 16-bit minicomputer TI-990 into a 
home microcomputer called TI-99/4, which was deemed a failure and replaced 
with TI-99/4A, which was also deemed a failure and (somewhat) replaced with 
its miniaturized 8-bit form, TI Compact Computer 40 (CC-40), which was such 
a failure they didn't even manage to release an official cassette tape drive 
for it (hoping to release a floppy drive instead, they even made a promise 
on the box about it that never came true), and opted for further 
miniaturization of the concept, releasing TI-74 BASICALC in 1985 and TI-74S 
in 1986. Unlike its predecessors, the 74 got а decent set of official 
peripherals and add-on cartridges (none of which are possible to find here 
nowadays, of course), proved to be quite reliable over time and is generally 
considered a success. Since then, however, Texas Instruments started 
developing their graphing calculators like the TI-8x lineup and others on 
the Zilog Z80 or 68k architectures instead of their own, switching to ARM in 
mid-2000s for their highest-end models. That's why TI's own in-house 
architecture really ends with TI-74S. And this final form offers an 8-bit 
CPU (TMS70C46), 8K RAM and a single-line scrollable 31-character display 
with the space for 80 characters total. Well, at least it can into lowercase 
letters, most similar machines of the time just shouted at you with 
permanent uppercase like the first Apple II iterations. And most 
importantly, nothing at all had happened to this display since 1988. And the 
contrast adjustment wheel functions as expected too. The machine that's 
older than me really works like new on four rechargeable AAA cells. I am 
truly impressed.

What are the differences between the BASICALC and S versions of TI-74, you
might ask? As far as I know, there are only three of them. First, and that's 
the most obvious one, the S keyboard doesn't have all those overlays that 
BASICALC has. This was done so that the OEM customers the S version was 
shipped to could label the keys the way they saw fit for their custom 
software ROMs. For the same reason, the quick reference sheet in the S 
version is always customized (in my case, it was a quick German manual on 
how to use the VGH cartridge module). Second, for the sake of customization, 
the S version allows the cartridge to autoload its contents on the power-on, 
yes, I found out that the BASICALC version didn't allow that. Third, and I 
have no way to verify this, rumors are that the S version allows adding 16K 
RAM cartridges while the BASICALC version only supports adding 8K at most. 
Not sure how practical this is since RAM cartridges were always 
battery-backed and the battery there had an uncommon size (CR1620 or 
something like that), but yeah, these are the only TI-74 version differences 
I could find about online. So, other than that, everything applicable to the 
BASICALC version is valid for the S version, and vice versa. So, from now 
on, I'll just refer to my TI-74S as just the 74.

Unlike its "older siblings", the 74 supports two modes: BASIC (programming)
and CALC (scientific calculations), hence the initial BASICALC moniker. I'll 
be honest, without the key overlays, the CALC mode is harder to grasp but 
still doable. In the BASIC mode, all the overlays give you are shortcuts to 
some most-used BASIC keywords via the FN key, but even the BASICALC version 
doesn't have all of them printed, so it's better to just memorize those you 
use most often. As far as I understand, the BASIC dialect here is quite 
advanced compared to most handheld PCs of the time and descends directly 
from the TI-99/4A Extended BASIC through the CC-40 (minus graphics, sound, 
machine code debugging, direct memory manipulation and custom glyph 
definition capabilities). The programming manual is now available online and 
easy to find, so I have downloaded it (along with the general user manual 
and technical reference) and started studying this BASIC dialect. I'm pretty 
sure that some of my next phlog posts are going to cover various aspects of 
programming on this machine, because what I'm seeing so far is pretty 
fascinating.

Another interesting feature is the Dockbus port on the back of the computer.
This is not a new invention and is just a single-line rearrangement of the 
CC-40's Hexbus port, however, the Hexbus had 8 pins and the Dockbus has 10. 
And it turned out that the two additional pins are actually pretty 
important: pin 1 (along with pin 10, which is Ground) allows to power 
external peripherals from the 74's batteries, and pin 2 (again, along with 
pin 10) allows to power the 74 itself from external sources. And it looks 
like the voltage of an external source can vary from 4.5 to 6.3 volts (4.5V 
is when the "LOW" indicator shows up). It's easy to see that 5V also is 
within this range. So, guess what I did? Right: took a useless charge-only 
USB cable, cut off the microUSB plug and soldered a black Dupont connector 
to the minus wire and white to the plus wire. Now, whenever I plug the white 
connector into Dockbus pin 2 and the black one into Dockbus pin 10, I can 
power the device via USB even without any batteries. And guess what I tried 
next? Right, connecting this makeshift USB power cable to one of the weakest 
foldable solar panels I have. And yes, it worked. So, now I have a backup 
scheme to power the machine whenever I run out of charge in my rechargeable 
AAAs and out of backup AAAs: a USB power bank or even a small foldable solar 
panel that won't give a reasonable amount of power to a modern smartphone. 
Do you know any other retro computers that would allow you to easily do such 
things? Of course, this isn't everything I'm going to do with Dockbus, but 
it's the most useful thing I have already done with it for the time being.

The main question though is, why did I need this machine and what am I
planning to do with it? Well, I see it as a nice, totally offline and thus 
untraceable, low-power tool for helping with tedious field cipher operations 
like generating keyed alphabets, Polybius square or tabula recta 
permutations from keyphrases, or even main encryption/decryption operations 
in an airgapped environment. It would allow for the same operations you 
might do with pen and paper (so the counterparties without such a machine 
would still be able to communicate with you), but faster and less 
error-prone. It can also be used as a moderate volatility notetaking tool 
using the BASIC's DATA statements: as long as the batteries are there and 
you don't type the NEW command, every program line remains in the memory. In 
case of emergency though, everything on the device can be deleted as easily 
as typing NEW ALL. Add power source versatility and overall reliability to 
the picture, and you get a perfect field computer for those who need to stay 
off the radars. And I kid you not, there even was a special modification of 
MK-85 called MK-85S, which was a government-issued airgapped cryptographic 
tool with a custom ROM and Cyrillic keyboard layout. What prevents us from 
making the same on a stock TI-74 if we want to?

Furthermore, once you know the language, such a machine becomes a canvas to
unleash your creativity in such a seemingly limited space. They say that the 
Internet opened a whole world previously unknown to every individual user, 
well, I could say that devices like this one, being fully offline, contain 
their own worlds inside themselves. And these worlds are sometimes no less 
interesting to explore. I remember playing around with MK-52 and finding 
ways to enter "unenterable" hexadecimal characters and illegal program 
sequences into memory, even created a sort of a virus that would hang the 
calculator once loaded from the EEPROM and accessed via registers. And those 
were 15 registers and 104 bytes of program memory (and 512 bytes of EEPROM) 
and a digits-only calculator display, imagine what you can fit into the 
entire 8K RAM with full ASCII capabilities if done right. Of course, this 
can only be done if you think outside the box of colorful graphics and other 
multimedia fed to you in the modern information age. The 74 is pretty much 
an antithesis of the nowadays trend of consuming more resources to do the 
same things, so it aligns with my low-power computing philosophy better than 
most devices in my collection.

And no, using a modern smartphone or tablet to do the same kind of
programming, even with an external keyboard, is nowhere near as convenient 
and secure as a dedicated QWERTY device that doesn't consume extra power for 
the display you don't need and for constantly trying to connect somewhere 
without your consent. It is, in fact, a bit of a problem that any 
portable/pocket PC you can buy nowadays is connected by default, sporting 
Wi-Fi and/or Bluetooth and/or cellular, and you don't even have a choice to 
have neither of them anymore, and usually have no control over what happens 
under the hood. Yes, TI-74 has a ROM chip with irreplaceable firmware too, 
but it physically cannot spy on you and doesn't even theoretically have 
enough hardware capabilities to do so. Besides, the technical document 
contains full device schematics that can be verified just by opening it up. 
No "security through obscurity", no hiding of the truth from the customers, 
maximum honesty and repairability. Something that nearly every new piece of 
consumer electronics is missing, including the current generation of TI 
calculators as well. That's why, by the way, I'm not interested in getting a 
TI-Nspire or even a TI-84 Plus as much as I'm interested in further studying 
what this TI-74S really can do. And I'm pretty sure it can do enough 
interesting stuff, so you can expect more phlog posts from me on the topic 
of this machine in the future. For now though, that's all I can tell. See ya!

--- Luxferre ---