TI 990 architecture

James B. DiGriz jbdigriz at dragonsweb.org
Thu Oct 11 20:40:30 CDT 2007

James B. DiGriz wrote:

> There is at least one other 100-contiguous-pin bus TI used, in the 
> DS990/1 computer/771 terminal.

Well, something bothered me about this, so I opened the hood (er,
bonnet, for our UK list members) of my 990/1 (literally), and it has, in
fact, an 86-pin backplane. Oh well, score one for bit rot. Actually, 
two. I also looked again at one of the VPU200's I have. It has 16Kw, not 
64. 4116's, not 4164's.

What's interesting about the 990/1 is it has 2 9900 boards in it, one 
main CPU and the other for file I/O. Thing should zip right along, but 
that will have to wait until I hook some drives up to it.

While I was at it, I opened up an XDS/22 TMS320C25 emulator system I
have, since it has an interesting SE9996JD processor along with a 'C25,
and it also has an 86-pin backplane, although the pins are split between
two card-edge fingers.

I have no idea yet if the busses are anything alike beyond
that, but the 9996 looks exactly like one of the purple ceramic 9900's,
64-pin DIP and all. Given the nomenclature, I can only speculate that it
may be the equivalent of a 9995 without the multiplexing of the data
bus. I haven't been able to find a datasheet, but I'm going to do more
investigating to see whether it can drop-in replace a 9900, which
might be interesting. Anyone know whether this can be done and/or tried 
it? Also, has anyone here used both the TM990 and AMPL development 
systems enough to tell me if they aren't essentially the same software-wise?

Thx in advance.

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