Reasons for scarcity of working TI-58C machines

[Steve Simpkin]

I found it interesting that TI chose to use an off-the-shelf CMOS RAM chip from RCA, Toshiba or NEC in the TI-58C instead of making a CMOS version of their existing memory chip used in the TI-58/59. To use this commercial RAM chip they had to make an additional chip to interface to it. Because of this there is quite a difference in the circuitry between a 58 and a 58C. I also wonder if these early CMOS RAM chips were less durable over time than the PMOS chips used in the non-C version.

http://www.datamath.org/Sci/WEDGE/TI-58C.htm