One cannot solve it all. Despite a lot of effort, some of the work was never done. Some TI-59 secrets remained sealed... forever. Or maybe you have a solution?
|Eight Hierarchical Internal Registers (HIR) were mostly used as additional data storage. All HIR instructions were decoded, except the HIR 20 instruction used in TI-59's firmware. TI-59 patent briefly mentioned HIR 20 as 'conditional return'. It is not known whether this return could be used outside the firmware. The HIR 20 instruction appears to have no effect, but...
|HIR stack pointer
|HIR registers were supposed to be used internally, for complex calculations, printing and statistic functions. In time, they became scratch space for programmers, which was sometimes inconvenient - use of the internal register could interfere with pending calculations. Nobody ever found a way to access the HIR 'stack pointer', i.e. the internal register containing the number of the last HIR register used by the system.
|Texas Instruments designed a simple, but effective security system. You just used '-1 Write' to save the program on the magnetic card. The program from the protected card could be loaded and executed, but not analyzed, traced or modified. Nobody ever found a 'clean' way to unprotect the program. There is a Blachly-Swinnen procedure of putting some Scotch tape on the card, which would actually solve the problem (see TI PPC Notes v5n3p2), but this "hardware" solution is a bit unorthodox. On the other hand, HP-41C users found quite a few ways to read the Private (protected) program using only a keyboard. Is it possible to access internal register 11 and the 'security code' mentioned in the TI-59 patent? Nobody knows...
|Not really a secret, rather an unfulfilled wish. Texas Instruments was willing to produce a custom solid-state software module, so members of the TI PPC Club and Programbiten dreamed about a ROM containing selected utility programs... We never assembled a module nor put together the $12,000 needed for 250 units. On the other hands, HP-41C users, members of PPC Club, published a marvelous PPC ROM, 8K of highly optimized software accompanied by a 5000+ page manual. It took an enormous effort and it interrupted the PPC Journal publication for nearly a year. So it was probably safer not to try.
|Another unfulfilled wish... there are emulators for most of the personal computers and even calculators... TI-59 emulators is still 'under development'. But try this one, or this one for PocketPC...