Differences between model 1, 3 and 4

[cjs]

So what did the $300 Model III upgrade kit consist of? My tech manual mentions nothing about the Level I version. It does state that the first RAM bank is the only one that can support 4K, so I always assumed the upgrade was nothing more than a ROM and RAM swap

From looking at the first catalogue entry for it, and noting that the upgrade is exactly the same price as the price difference between the Level 1 BASIC/4K and Model III BASIC/16K, I would guess that it's just a RAM and ROM swap. Weirdly, the price of that kit remained at $299 for years, even as the 16K RAM expansion alone dropped to $99 and then $49. (And, well, the base machines in each configuration remained at $699 and $999, too, so I suppose they reckoned that, Level 1 BASIC being so useless, they saw this as a good way to get eke some profit out of a market where prices were otherwise falling rapidly.)

 

[Eudimorphodon]

It kind of surprises me that any private individual ever bought the 4K Level I Model III. I would have thought it would have been almost completely an educational institution special. The Level I Model I made sense in 1977, but by mid-1980 when the III came out if you wanted a computer that nerfed there were cheaper options.

 

[krebizfan]

IIRC, the Model III did not support Level I BASIC cassette interfaces. The 4K Model III was useless. It didn't even make much sense for Tandy to sell since 16K RAM was the same price as 4K RAM so Tandy would have had to eat $300 on each unit.

 

[Eudimorphodon]

IIRC, the Model III did not support Level I BASIC cassette interfaces. The 4K Model III was useless. It didn't even make much sense for Tandy to sell since 16K RAM was the same price as 4K RAM so Tandy would have had to eat $300 on each unit.

They probably saved at least a *measurable* amount of money on mask ROMs, since the Level I had just 4K of ROM verses the 14K in the Level II, but yeah, I'm sure the BOM cost differences for a 4K Level I verses a 16K Level III was laughably tiny. (The Commodore VIC-20 came out a month before the Model III for $299 and it has *20K* of ROM in it, so assuming Tandy was buying BASIC ROMs in anything like reasonable quantities it seems like they could have put *both* Level I and Level II in every machine and made them switchable if they'd wanted to without significantly affecting the retail price.) That's why I'm pretty convinced the only reason they sold it was so they'd have something on offer that was directly compatible with educational courseware that had been built around Level I.

I think I've grumbled about this before, but I'm convinced that the price of the Model III was one of the reasons why Radio Shack's market share started falling after they discontinued the Model I. The price of the 4K Model III was $200 more than the equivalent Model I ($499 vs. $699), while the 16K Level III configs were $849 and $999 respectively. The Model III has a few improvements, like a printer port and sockets for more memory built in (it also comes with lowercase standard, but it pains me to even count that since the cost of that improvement was under $2 by 1980) and I imagine the plastic all-in-one case probably cost a *bit* more to make than the separate keyboard and TV cases of the one, but... if they were actually making a profit at $699 for the lowest level configuration I think they should have sold the Level II 16K for that. (If they *really* had customers that needed Level I they could have sold a 16K Level I for the same price special order.) Jacking it up $150-$200 for such minimal enhancements at a time where everyone else was pushing more features for *less* money than last year's model was a really bad look.

 

[kiwisincebirth]

But perhaps even more annoying, the Model I's keyboard was missing a number of keys that were often pretty important for use of remote systems. The Ctrl key is the biggie there (imagine using a remote CP/M system without being able to type even Ctrl-C), but Esc is another one commonly wanted, and printing characters from '[\]^_`{|}~' (all missing on the Model I) are also often enough wanted.

The characters from '[\]^_`{|}~' are actually encoded by the keyboard matrix in the missing keys after "Z", ie. if you add switches to the matrix, there was noting else to do, the ROM routine's just worked. The Dick Smith System 80 (I had back in the day), had an additional row of cutouts in the metal above the numbers. So it was n easy job to install and wire additional keyswitches.

 

[kiwisincebirth]

Dick Smith System 80 • Evolvable Me

www.grahamlea.com

 

[kiwisincebirth]

a better link (see second picture)

System 80/Video Genie/PMC80 - Images

 

[Bruce Tomlin]

This is all fixable, since the Model I has a software-scanned keyboard; the first obvious change would be to make the down arrow into a Ctrl key.

actually it used shift-up-arrow (or was it shift-down-arrow?) as a ctrl key

 

[cjs]

The characters from '[\]^_`{|}~' are actually encoded by the keyboard matrix in the missing keys after "Z", ie. if you add switches to the matrix, there was noting else to do, the ROM routine's just worked. The Dick Smith System 80 (I had back in the day), had an additional row of cutouts in the metal above the numbers. So it was n easy job to install and wire additional keyswitches.

Oh, interesting. Yeah, I had a quick look at the keyboard input scan code at $3E3 in the Level I ROM and from the way it deals with assigning values to the letters, yeah, it will just carry on after z through {|}~ and DEL, and of course Z[\]^_ if shifted. Nice!

And looking at the keyboard schematic, it's probably only a few bodge wires to wire these things in! Though finding a place to put those keys on a Model III would be a bit of work. I suppose you might try to unsolder some of the keypad keys to use them instead as those extra keys, but that would be a bit of work, in my experience with that sort of thing.

And of course it still leaves you with needing a new scan routine for Ctrl, anyway, at which point you would probably be just as well off (possibly even better ergonomically) using certain ctrl-punctuation sequences for the extra characters.

 

[cjs]

actually it used shift-up-arrow (or was it shift-down-arrow?) as a ctrl key

Oh, so it did! Holding Shift and Down-arrow together subtracts $60 from the shifted value (which in turn was the unshifted value plus $20). This happens at the end of the $040B routine just after the one I linked above.

How did I go so long without ever knowing this? Argh!

Unfortunately, this applies only to the alphabetic keys; the code dealing with Shift for the numeric/symbol keys at $0429 doesn't check for Shift-Down-Arrow, so you can't use that to get a third set of codes for the numeric/symbol keys. Which is too bad, because otherwise you'd then have a dozen "weird" codes that your program could then interpret as the missing ASCII characters. Ah well.

 

[cjs]

They probably saved at least a *measurable* amount of money on mask ROMs, since the Level I had just 4K of ROM verses the 14K in the Level II, but yeah, I'm sure the BOM cost differences for a 4K Level I verses a 16K Level III was laughably tiny.

I'd expect that the largest part of the cost was actually the licensing fee paid to Microsoft for Level II BASIC. I wonder how much it was.

IIRC, Commodore was the only company that ever managed to get a flat rate, rather than per-unit, license to MS-BASIC. Though the trs-80.org page does state in footnote 6:

Microsoft had no part in the conversion [of Model I Level III BASIC to Model III BASIC] although, according to John Roach, they received “additional compensation” for its use in the Model III. Bill Gates said that Microsoft received “an on-going yearly fee” for Model III BASIC, further stating that it was “strictly bounded.”​

which isn't really clear, and could be read as they received the standard Level III fee plus something additional for the Model III version of Level III.

 

[Eudimorphodon]

IIRC, Commodore was the only company that ever managed to get a flat rate, rather than per-unit, license to MS-BASIC.

So it looks like Apple also got AppleSoft for a flat fee of $31,000, although their deal was for eight years, not perpetual, so they had to renew it in 1985.

I guess it’s really hard to say how much Tandy was paying for it, or at least it’s a factoid that has somehow escaped the Internet’s search magic? I would be skeptical, though, that it was that much even if Tandy was paying per unit. (Apparently Commodore got their flat rate after passing on an offer of per unit royalties of only three bucks a head.) That comment from Gates about the fee being “strictly bounded” makes me suspect Tandy negotiated a deal similar to Apple’s but structured as a “yearly subscription” instead of a lump sum for eight years.

Of course, Tandy *was* notoriously tight-fisted, so if it was per unit, even if only $3 a head, there would no doubt be execs in the company that would want to milk whatever they could out of it.

 

[Bruce Tomlin]

I still want to know how much Vtech paid, and to whom... if anything at all. They reused the TRS-80 ROM directly, wiping over the sections they didn't need to add their own custom stuff, but most of it is still the same bytes at the same addresses. I don't know exactly when they were using it (wiki says the Pre-Computer 1000 was mid-1988), but did Microsoft or Tandy care anymore, or even know about it while they still cared?

 

[Eudimorphodon]

I don't know exactly when they were using it (wiki says the Pre-Computer 1000 was mid-1988), but did Microsoft or Tandy care anymore, or even know about it while they still cared?

VTech was making these weird hybrid machines which were basically what you’d get if you left a very lonely TRS-80 Model I and Color Computer alone in the back room of a Radio Shack from 1982, I would guess the Pre-Computer and friends’s BASIC is a direct descendant of that? Apparently these were intended to compete with EACA’s Color Genie, which likewise took Model I BASIC (filtered through the “fully” TRS-80 compatible “Video Genie” clone) and minimally hacked it up to support the different video system.

EACA was found guilty, via their US reseller, of violating Tandy’s copyright but, confusingly enough, not Microsoft’s; EACA *had* paid Microsoft a license fee for “generic BASIC” which covered code compiled from the same source with the same entry points as Tandy, but this license *did not* cover about 2K’s worth of code which was specifically written to support Tandy’s hardware. Instead of rewriting those parts EACA just ripped them off (which no doubt improved compatibility), and after losing the lawsuit they agreed to stop selling the Video Genie… in the US. Apparently Tandy didn’t think it worth their time to pursue them in other countries, which considering it was 1983 at this point kind of adds up.

(If we believe that EACA actually did have that license to “generic” BASIC, and the infringing parts were mostly TRS-80-specific initialization and I/O code then it’s conceivable that maybe the *Color* Genie *was* “legal”, since those are the parts you’d need to change or comment out if you radically changed the hardware/memory map?)

Of course that’s EACA, not Vtech. Both were based in Hong Kong, which was a hotbed of unlicensed cloning in the early 80’s (in addition to TRS-80’s they made Apple clones, many of the first PC clones before legal BIOSes from the likes of Phoenix were available, etc.) so maybe they never had a Microsoft license at all, but… again, if EACA really *did* have one it’s not much of a stretch to guess MS might also have rubber stamped one for Vtech. I’m pretty sure Vtech did ink an actual legal license for the AppleSoft clone in the Laser 128 (to cover their butts when Apple inevitably came snooping) so… if they didn’t have the rights in 1982 it wouldn’t surprise me if their later license for 6502 BASIC included some clauses to cover usage of the Z80 code, perhaps including “back payment” for prior activity.