Author Topic: EEVblog #1169 - TI 1972 Computer Interfacing  (Read 3545 times)

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Online EEVblog

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EEVblog #1169 - TI 1972 Computer Interfacing
« on: January 16, 2019, 07:49:45 am »
How did you connect to a time sharing computer in 1972?
Teardown of the Texas Instruments TI Silent 700 model 745 terminal with acoustic coupler modem.

 
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Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #1 on: January 16, 2019, 09:05:32 am »
When I was co-op engineer in college, we used these terminals.  Ours were the version with two tape drives.  The application was to generate configurations for microwave relay system racks.  One drive would prompt the operator for various options.  The responses were written to the second drive.  That tape would then be downloaded to a Univac 1108 mainframe that would punch a card deck that was sent to an IBM mainframe that produced another card deck of all the parts that would be needed to build the system.

The problem was that if any operator errors or bad or conflicting entries were done, the whole process would have to be repeated.   It could take an engineer a week to generate a valid rack configuration.  So, I changed the program (without asking anybody) to skip the tape drive step and do an interactive configuration dialog with instantaneous error checking and punch the first deck directly.  It reduced the time to generate a valid (and error-free) configuration to under 30 minutes.

Another change was to read the parts database directly.  The original programs would query the database in a way that simulated reading punch cards... which the Univac charged around 25 cents per "card."  I changed the way the data base was read which bypassed the card charge (which could be around 1000 "cards" per rack. 

Surprisingly management was rather furious, but got over it after realizing the savings and god-like praise from the configuration engineers.   Over several years there was not a single report of the system generating a bad rack configuration (and anybody collecting the bounty offered for finding a bug that would generate an improper configuration)... it saved the company millions of dollars.
 
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Offline jancumps

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #2 on: January 16, 2019, 09:10:31 am »
I would have drooled all over that service manual non-stop. My first stereo came with the schematics and all the corners are torn from constantly looking at it.
 

Offline floobydust

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #3 on: January 16, 2019, 09:11:44 am »
Model 745, 1972 $1,995 in today's dollars is about $12,000 !
I see a lot of expensive innovation in it. The SMPS, a portable 8080 device, no ink ribbon (thermal printing tech?).
Looks like an 8-track or cassette tape motor for the fan.
 

Offline coppice

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #4 on: January 16, 2019, 09:19:23 am »
The slow mode was 110 bps, for compatibility with the dominant ASR33 of the day. The models with an RS232C socket on the back worked up to 1200bps on that port. The acoustic modem was limited to 300bps.

The "here is" key sent a break - basically a UART framing error, which the receiving end would register without decoding the serial stream, and wake up.

The version in the picture with 2 cassette tape drives was one of the mainstays of early microprocessor system development. We used them a lot when developing assembly language code, before people like Intel and Motorola got their 8" floppy disk based development systems working.

« Last Edit: January 16, 2019, 10:35:36 am by coppice »
 

Offline Jr460

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #5 on: January 16, 2019, 09:38:34 am »
None standard DB-25....   Dave, shame on you.

RS232 on DB25 was the standard, the DB15, or DB9 were not.

Anyway, used one in the mid 80s.   You would use it as the console of larger system so if it crashed you had the info on what happened on the console.   Also when doing a special install you wanted that rather than CRT so you had a good record of what you did.

But beyond that for many years we would use a DEC LA120 for the console of systems.
 

Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #6 on: January 16, 2019, 09:39:31 am »
Model 745, 1972 $1,995 in today's dollars is about $12,000 !

Cost of a print head replacement was around $500...
 

Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #7 on: January 16, 2019, 09:41:27 am »
Dave,  your printing problems could just be old paper.  Try some new paper... but you might void your warranty.
 

Offline Fungus

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #8 on: January 16, 2019, 10:20:07 am »
Is that a Motorola transistor in a TI power supply?  :popcorn:
« Last Edit: January 16, 2019, 10:35:31 am by Fungus »
 

Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #9 on: January 16, 2019, 10:42:57 am »
Is that a Motorola transistor in a TI device?  :popcorn:

Ahhh, yes.  Motorola devices.   The company that I worked for got a HUGE contract to build a state of the art telecommunications/phone network for a large middle eastern country.   They had to remove the Motorola logo from every single device in the system... zillions of them...  picture a room full of women with electric erasers.  Why, you ask?  Well, I was told it was because a Jewish person was on Motorola's board of directors!   No idea if they had to also remove the "MC" from the device numbers.
 

Offline wilfred

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #10 on: January 16, 2019, 11:06:12 am »
I have one of those somewhere that I picked up for $10 on Ebay a few years ago. Mine is much smaller because it doesn't have an acoustic coupler. I must fish it out and try it. Mine will probably have the same print issues. So I was hoping to see you attempt to resolve them.

According to the manual http://www.decadecounter.com/vta/pdf/TI%20Silent%20700%20Model%20745%20Operating%20Instructions.pdf the HERE-IS key transmits the contents of the optional answer-back memory. Maybe that is the empty socket.

That same website had a document about the ACCUTRON mechanism that might interest some. http://www.decadecounter.com/vta/pdf/accutron_chronometric.pdf

Also there were manuals on the HP 2114 computer, various valves and HP calculators. Not saying it can't be found elsewhere but who knows.
 

Offline chickenHeadKnob

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #11 on: January 16, 2019, 12:10:31 pm »
Model 745, 1972 $1,995 in today's dollars is about $12,000 !

Cost of a print head replacement was around $500...

And that's why they were never very popular in my neck of the woods, compared to say LA DECwriters.

Dave gains extra street cred with his eagle eyes and laser like focus for noticing those odd-ball sockets. Those were made by TI! Yes Texas Instruments made dip sockets. I have a new-oldstock narrow dip 20 pin wire wrap socket in my hands right now and they don't have any insignia or markings to give that away. The 600mil sockets have a small Ti on the underside. I always kept a few of these wire wrap length wide dip sockets for a special end use. Alas they have gone to the same place as the dodo and all of those useful and unique jfets from that era.

Gather around the campfire boys and girls while Grampa explains what they are good for.  You see with the wipers oriented in the 'wrong' way they are the only sockets into which you can plug a 3M ZiF socket directly, without bother. Well there is a small amount of effort as you have to remove the plastic top cover of the TI socket with your fingernail or exacto knife.
You see the ZiF socket pins are also oriented-flat in the wrong way. Match made in heaven, the 3M sockets  fit snug. They can not be plugged into a machine pin socket which was always my first choice in sockets..

You need a (TI) socket like this if you are making a DIY eprom programmer and want a simple and convenient way to connect the ZiF socket pins to the underlying circuit through an enclosed case. What you do is solder the TI socket to your board in such a way that the top sits just proud of the surface of your case. Then you just plug the ZiF socket into that after the case is assembled. Neat and easy-peasy. This is useless knowledge now that the TI sockets are unobtainium. |O

pictures to follow when if gramps can get his phone to cooperate.

 
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Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #12 on: January 16, 2019, 12:42:28 pm »

And that's why they were never very popular in my neck of the woods, compared to say LA DECwriters.


But DECwriters are not very portable...  the Silent 7xx machines were meant to be easily carrierd.. except for the desktop models.

Also, the paper for the Silent 700'd was also rather expensive.  The printheads seemed to last for a case or two of paper.  I think that is why most of them were leased (with maintenance contracts).  I watched our TI guy come in and replace a printhead.  I shoulder surfed the number that he dialed to their test system.  He left his login details on the new roll of paper he installed... password was not obscured.  That made it easy to test the machine later   >:D
 

Online EEVblog

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #13 on: January 16, 2019, 02:39:52 pm »
I would have drooled all over that service manual non-stop. My first stereo came with the schematics and all the corners are torn from constantly looking at it.

I had the service manual for my Tandy 1000 with all the schematics and datsheet, it was paper gold.
 

Online EEVblog

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #14 on: January 16, 2019, 02:42:47 pm »
Dave gains extra street cred with his eagle eyes and laser like focus for noticing those odd-ball sockets. Those were made by TI! Yes Texas Instruments made dip sockets.

Wow!  :o
 

Online EEVblog

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #15 on: January 16, 2019, 02:47:37 pm »
None standard DB-25....   Dave, shame on you.
RS232 on DB25 was the standard, the DB15, or DB9 were not.

It's a DB15 and I said non-standard
 

Offline johnlsenchak

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #16 on: January 16, 2019, 03:08:54 pm »


What  you have there is a  over priced  typewriter   that  connects   the serial  port to   a  distance mainframe .

Think  of the computer technology  today that you can get for $1995   compared to that archaic   piece  of junk ;D
John Senchak "Daytona  Beach  Florida "
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Online helius

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #17 on: January 16, 2019, 04:38:33 pm »
According to the manual the HERE-IS key transmits the contents of the optional answer-back memory. Maybe that is the empty socket.
That's correct! This was used to identify the location of the connected teletype ("Building 100, terminal pool 6") in response to a ^E from the host. This could also be used to tell the host something about the terminal's capabilities (later, the ANSI X3.64 standard supported specific capability information).
https://en.wikipedia.org/wiki/Enquiry_character
« Last Edit: January 16, 2019, 04:53:36 pm by helius »
 

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #18 on: January 16, 2019, 05:07:28 pm »
Dave, you didn't mention the real reason that acoustic couplers were used. In the 1960s, there were no standard modular phone connectors, and the only devices that could legally be connected to the phone system were rented by the phone company (including phones, special multiline systems, and modems, all of which were billed at monthly rates). It was only after the Carterfone decision that you could privately own a modem electrically connected to the network.
 

Offline boffin

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #19 on: January 16, 2019, 05:46:43 pm »
None standard DB-25....   Dave, shame on you.
RS232 on DB25 was the standard, the DB15, or DB9 were not.

It's a DB15 and I said non-standard

Surely you mean DA15?  The 2nd letter is the case size, so in the 'normal' dual row config D shell connectors are:
DE9
DA15
DB25
DC37
DD50
Also, IIRC it's 20mA loop, and not RS-232.  Yes you read that right, it pre-dates RS-232 !!!!!

As for the "Here Is" key, it sends the programmed answerback, which can also be sent by the remote side sending a Control-E (ENQ - Enquire).  It was a cheap/easy way for a remote side to detect a device, or send perhaps a short loginID or something like that.  Terminals like the VT100 also had a builtin answerback (which we would abuse in college by setting it to "^log^m").  That empty socket is for a PROM it would be burned onto. 


FAST = 300 baud = 30 characters/sec of (start + 8 data + stop)
SLOW = 110 baud = 10 characters/sec of (start + 8 data + 2 stop)
and the 8 data could be 7 data+parity

I last used one of these in the mid 1980s, it was still the cheapest, most portable printer you could find.  Sure an LA120 was faster, but it was huge, and decidedly non-portable.



Lastly to the loser that in here said "archaic piece of junk", we wouldn't have the stuff we do, without innovative stuff like the Silent 700.

Boffin at play https://snafu.ca/
 
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Offline blacksheeplogic

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #20 on: January 16, 2019, 06:03:50 pm »
No need to mock the device, for some applications a physical print was preferred. For example systems I worked on often the console was a printer/keyboard. Early on I had to send programs for data entry and most processing was batch anyway.
 

Offline coppice

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #21 on: January 16, 2019, 11:36:48 pm »
No need to mock the device, for some applications a physical print was preferred. For example systems I worked on often the console was a printer/keyboard. Early on I had to send programs for data entry and most processing was batch anyway.
The Silent 700 was a thing of beauty in its day. That's because it was the key alternative to an ASR33 teletype, which was a truly awful clunky noisy thing to have to use all day.
 

Offline SeoulBigChris

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #22 on: January 17, 2019, 01:28:20 am »
I used this at Ga Tech in the very early 80s to connect to the campus computer mainframe. We had it in the ham radio club, and used it for homework and sometimes for logging radio contests.
 

Offline IanMacdonald

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #23 on: January 17, 2019, 01:57:49 am »
I think we tend to forget just how insanely expensive it was to do anything with computers back in those days. At uni we got to use the mainframe for small jobs, but we were always reminded that it cost £5 a MINUTE to run the thing. Anyone whose program got stuck in a loop was not popular. (Don't ask me how I know...) 
 

Offline texaspyro

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Re: EEVblog #1169 - TI 1972 Computer Interfacing
« Reply #24 on: January 17, 2019, 03:37:51 am »

SLOW = 110 baud = 10 characters/sec of (start + 8 data + 2 stop)


A lot of 110 baud systems used 1.5 stop bits...
 
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