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Mitra 125

I would love if there were more people interested in the Mitra-15 computer, so I created some code in order to interest people in improving it and hopefully make a push request on SIMH in 10 years.
This code is currently a nightmare as it's a SIMH SDS 940 base modified to described (really badly) a Mitra-15, it compiles but is completely unsusable. There are lot of FIXME in the code and I expect that it will be difficult to fix them! Maybe someone smarter than me will rewrite this mess.

The most modified file is mitra_cpu (previously sds_cpu.c),c, mitra_sys.c, mitra_defs and mitra_stddev.c are modified to a less degree. I think I didn't modify the other files otherwise than changing their naming from sds_* to mitra_*.

I made a mistake: I didn't use the official SIMH but OpenSIMH (I guess) to base my code. Hopefully they are not too different.

github.com

GitHub - JPLeRouzic/Mitra-15-for-SIMH: An attempt at creating a branch for Mitra-15 in SIMH. Works in progress.

An attempt at creating a branch for Mitra-15 in SIMH. Works in progress. - JPLeRouzic/Mitra-15-for-SIMH
github.com github.com
 
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Re MSB = bit 0:
Seems like the Texas TMS9900 also does this. I assume that the Texas minicomputers also does this.
 
MiaM said:
Re MSB = bit 0:
Seems like the Texas TMS9900 also does this. I assume that the Texas minicomputers also does this.
Click to expand...
Yeah, the TMS9900 is essentially the TI990 reduced to a single chip (not quite, but close enough). So they both use the same bit numbering.
 
So I managed to write some code that pretends to be a SIMH Mitra-15 simulator.
Yet I don't know, not only how to test it but also how to enter and run Mitra-15 code, here is what I get:

Mitra 15 simulator Open SIMH V4.1-0 Current simh git commit id: 0dc9deca
sim> dep 0 2005
sim> dep 1 2503
sim> dep 2 0
sim> dep p 0
sim> run
fish: Job 1, './BIN/mitra' terminated by signal SIGSEGV (Address boundary error)
jplr@jplr-ghostbsd ~/D/2/M/simh-master [SIGSEGV]>

Can you give me some tips? (please assume I don't know SIMH)
 
Not sure about the specifics of any IBM/Bull/Sigma7/Mitra connection, but my uncle, an IBM EE from 1952 to 1985, based in primarily Endicott and Poughkeepsie, spent about a year in France in working with Bull engineers. He had been part of the development team for System 360/370 and later was administrator at IBM's Glendale Lab in Endicott. This French interlude was in the late-ish 60's I believe. Unfortunately he passed a couple of years ago so no longer possible to ask him for any details. He had a strong friendship with one of the Bull engineers that he had stayed with there and they corresponded for years.
 
firedome said:
Not sure about the specifics of any IBM/Bull/Sigma7/Mitra connection
...
This French interlude was in the late-ish 60's I believe.
Click to expand...
Thank you for your message; it's very interesting because it shows French political business strategies were unclear.
Bull and IBM were theoretically competitors, but IBM was the leading player in the French market at the time, they could have eat Bull without noticing it.

Was it because IBM studied a Bull acquisition? In early 1960' IBM had five separate lines of computers aimed at different market segments and entirely different from each other. Maybe IBM was interested to learn how Bull was managing the same problem. Bull's Gamma 60 (1958) was an atypical machine: its instruction set was geared towards managing electromechanical data processing machines, without system software. However its hardware was very interesting. The system 360 was IBM's solution with a beautiful architecture.

CII, the company that produced a version of the Sigma 7 (the 10070) and the Mitra computers, appeared ten years later, and its computers were understandable in modern terms.

Bull and CII later merged in 1975, but their history was tumultuous both before and after the merger, and they wouldn't have existed without significant public funding. They were bought and sold by several American companies.

Strangely, the political discourse hasn't changed: then as now, the talk is of merging small businesses to "meet modern challenges and international competition." As before, the French private technological sector depends on public subsidies. French politicians have replaced "France" with "Europe" and "United States" with "China."
 
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