The 99/4 & 4A have such a great place in my heart. One of my uncles worked for TI (he was the exec sponsor for the Speak & Spell.) My mom had a LINC for a while and my dad bought a TRS-80 when it came out. So when the 99/4 was about to be released, we got the full court press from my uncle: there's a new 16 bit computer with color and sound and all sorts of cool features.
So we bought a 99/4. Pretty sure we got the friends and family discount. Many don't remember the original 99/4 released in '79, but it was definitely a weird beast. In retrospect it was very clear TI couldn't decide whether it was a console gaming system to compete with the Atari VCS or a personal computer to compete with the Atari 800, Apple ][, TRS-80 or Commodore PET. Peripherals were originally (large) boxes that chained off the side of the main unit. We had a speech synthesizer, memory expansion, RS-232 interface and floppy controller, so we wound up buying a special cable to let us move the chain to a different part of the desk.
To a modern audience, the most interesting part of the confusion between being a personal computer or game console might have been TI's attitude towards 3rd party software developers. If you wanted to write software for the 99/4, the first thing they wanted you to do was to give them $10k. And this was back in the late 70s, when $10k was a chunk of change. Companies like Milton-Bradley ponied up the cash for a license and a dev system (which I think was a $25k 990 system.) I wrote a couple games for the Apple ][, put floppies in a zip-lock and sold them through the local ByteShop. I think I sold 10 copies. For a kid in Jr. High, the $50 in profit I made was real money. I could not even conceive of where I would get $10k for a license to make anything for the 99/4.
In '81, TI released an upgraded version called the 99/4A, which was mostly identical, but had the upgraded video chip (the 9918A vs the 9918) and lower case characters (actually small caps, but who cares.) Even though there was plenty of data to suggest this Nintendo-esque approach to 3rd party software was more of a games console thing than a personal computer thing, TI stuck with it. I think the beige models of the 99/4A that started coming out in '83 before they exited the market included scrambled entry-points to various OS calls to make it harder for people to make unlicensed software (didn't AtariSoft run afoul of this? or maybe it was ActiVision. I know one of the "big names" didn't want to pay for the license and thus didn't get the "secret" information about how to properly call I/O functions on the beige machines.)
My uncle participated in researching a book on TI's corporate history in the late 90s / early 2000s. I helped him out a bit and one day called the main corporate library asking for any public info they might have on the 99/4. They claimed TI never made a machine called the 99/4 or 99/4A and I must be thinking about the TI-84 calculator. Maybe they just wanted to forget the whole thing or maybe I had reached the calculator library. In any event, most of the people I talked with who were involved in the project thought it was a failure and don't seem to want to share their memories. This is kinda sad. I loved my little 99/4, quirks and all.