Seeking... TI TMS9902 ICs

Sean Caron scaron at
Sun Jan 4 10:15:07 CST 2015

Do you happen to have any leads on the title? I searched for TMS9900 on
Amazon and I'm just getting back a few TI publications. Sounds like
something I'd like to have in my antiquarian EE/CS book collection if I can
find it :)

I know a lot of the "family" ICs are just there for convenience and that in
principle it's possible to hook up basically any LSI UART (or combination
of discrete parts equating to a UART) to any CPU given enough glue... but
since it's my first time through with the architecture, I want to keep it
simple if I can :) OTOH, I guess upping the challenge level a little bit
wouldn't kill me. ;)

As you note, I don't think the TMS9902 was even used in the TI99/4a; I
looked at some high-res board pics and couldn't make it out. I do have
other UARTs in my inventory i.e. 6551, 6850, 16550, etc.

I'm definitely looking forward to it... my TMS9995s should be here pretty
soon so I can start fooling around.



On Sun, Jan 4, 2015 at 7:42 AM, John Wallace <johnwallace4 at>

> Dave Pitts' aforementioned page links to some 990 stuff at bitsavers. The
> stuff there is largely system level stuff.
> People whose interests are closer to chip level might want to have a look
> at the 9900 Microprocessor Series Family Systems Design Databook available
> at, if they're not already aware:
> A 2 inch thick book that contained pretty much everything you were likely
> to need to know about the 9900 family.
> One of the few other useful 9900 resources I vaguely remember was a 3rd
> party 9900 book which contained the source for an "instant input assembler"
> - a tiny line by line assembler which you could add to your PROM-based 9900
> debug monitor so you could enter small programs as source rather than hex.
> Neat. Can't remember name of author or of book, can't quickly find them
> either.
> I worked with 990/4 systems many years ago and there was almost no 9900
> family glue logic inside. As far as I remember, the /4 was designed before
> (most of?) the 99xx support chips came to market. So a serial card in a /4
> had a handful of chips doing what a 9902 would eventually do in one. Not
> sure about the video controller but the same probably applied.
> I have a vague recollection that the interweb has some decent writeups of
> the innards of the 99/4 home computer stuff (sorry, no pointers); from
> those, it might be possible to work out if the kit of parts on eBay is a
> plausible match for a 99/4 or similar volume market product.
> Have a lot of fun
> John Wallace

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