TI-74 (74S) custom ROM development and deployment

[gferluga]

Hi:

 

Where I can find information about custom TI-74 (74S) ROM development and deployment?

In Europe many insurance companies, most in Germany, use to deploy custom ROM modules with their software.

 

Thanks in advance.

 

 

[+Ksarul]

There was a whole custom programming ecosystem all the way back to the CC-40. Most of the custom modules for either system are seriously difficult to find, and are usually missing the documentation when you do find them, making analysis that much more difficult. I suspect they had a development box for the TI-74 cartridges similar to the one they used for the CC-40. I've seen a couple of the CC-40 dev boxes in the wild, but not the one for the TI-74.

[gferluga]

Well. I bought this one: https://www.ebay.com/itm/126053749969

Waiting to receive it within next days.

Looks like a modules cloner. But I'm not sure which type of ROMS.

Let's see when I have it in my hands ;)-

 

[+acadiel]

The TI-74 SDK was not made available to anyone outside of TI.  The custom cartridges were developed for companies by TI as a service, and then given to the end user from what I’m told by the designer of the system.  That device you purchased allowed the customer to duplicate the cartridge/deploy updates from a new revision that they received from TI.  (The cartridges were all flash).  

 

Commonly, insurance companies needed new rate tables distributed, and rather than send them 100 new carts, TI shipped them one new one, and the customer would then update all their field cartridges.

 

Some points that I see being discussed -

 

One engineer did the TI-74 port of the CC-40 code by himself, with one system engineer doing the calculator design (and the first engineer the calculator coding).  It took about six months from start to finish to do the TI-74. The CC-40 code was used as the foundation of the TI-74 codebase.  The engineer reworked the paging routines to be TRAPs instead of CALLs, removed various built in subroutines (the debugger, several poke/peek type instructions, etc)  to make space for the calculator mode, used the TMS70C46 variant to integrate the Hexbus into the processor itself, and the processor code ROM (4K) started with the CC-40+ ROM, which had the cassette recorder code built in.  (But not the hardware, which was provided by the CI-7).

 

For TI to release the internal development information for the 74, including the fixed address points for paging routines, etc, the one person that’s left would who knows about the 74 would have to review all the documentation to open source it.  That person does not have the cycles to do so, and TI will not do it otherwise.  (The 74 removed the banking lines.  To get the multi page stuff working for the 64k and 128k modules that were made by these 3rd parties, there’s assembly routines that must exist in the module memory space at identical locations and the paging circuitry is inside the module itself.)

 

Secondly, the 74 female cartridge connector is unique.  The spacing and pin count is not used by anyone else, and was only used by TI.  The molds were all destroyed and nobody else has replicated the cart connector.  It would have to be recreated.

 

Lastly, a difference between the TI-74S and the TI-74:

 

The TI-74S allows the cartridge to auto run, bypassing BASIC, has no calculator overlay, and CALL ADDMEM can add 16K of RAM instead of the 8K that the TI-74 adds.

 

Hope this helps.

 

 

[Eric Smith]

A frend worked for the corporate office of a business that had the TI-74 ROM internals documentation, which was several hundred pages IIRC. They had obtained it from TI, and they did develop their own custom code, and deployed it in EPROM modules for field sales use. They used the TI-74 for many years. Some years ago, my friend gave me the TI documentation. Unfortunately I no longer have it. If I had realized that it was not widely available, I would have made more effort to preserve it. Since my friend's company, which was not huge, had been able to get it, I thought it had been readily available. I'm working on getting another copy.

[gferluga]

On 11/6/2024 at 10:57 PM, Eric Smith said:

A frend worked for the corporate office of a business that had the TI-74 ROM internals documentation, which was several hundred pages IIRC. They had obtained it from TI, and they did develop their own custom code, and deployed it in EPROM modules for field sales use. They used the TI-74 for many years. Some years ago, my friend gave me the TI documentation. Unfortunately I no longer have it. If I had realized that it was not widely available, I would have made more effort to preserve it. Since my friend's company, which was not huge, had been able to get it, I thought it had been readily available. I'm working on getting another copy.

Thanks Eric!