Interesting HP processor circa 1974

[Andrew]

Noticed this on CPUShack. This is only 5 year after the US landed on the moon remember.

Andrew

[Brian Gaff (Sofa)]

Does anyone remember the home computer by Texas Instruments, the TI 99/4A, the name probably contributed to its lack of success. It was the first 16bit processor. It predated most of the 8 bit machines, but of course being non standard, it lost out due to nobody supporting it in machine code terms and so ended up as an oddity that had a stepped keyboard, a bit like a typewriter, and a cart slot for games. Brian

[Vir Campestris]

I considered buying one.

Interesting CPU - perfect for Fortran. Useless for C or Pascal.

Andy

[Graham Nye]

Ken Shirriff's blog has more on this processor:

There are other examples of reverse engineering ICs on his blog.

[mm0fmf]

Yes, but look how fast you could context switch on it!

You could emulate the missing hardware stack register using post and pre autoincrementing addressing on one of the GP regsiters.

However what contributed to its lack of success was the lack of software, the fact it was a 16bit machine crippled with an 8 bit memory bus (in 99/4 not the TMS9900) which slowed it a lot and it cost an absolute fortune.