Texas Instruments PLOT DEMO Solid State Software Cartridge (Prototype)

Date of introduction:  (1983) Display technology:  
New price:  $59.95 (MSRP 1983) Display size:  
Size:  1.8" x 2.0" x 0.50"
 46 x 52 x 13 mm3
Weight:  0.9 ounces, 26 grams Serial No:  
Batteries:  n.a. Date of manufacture:  wk 40 year 1982
AC-Adapter:   Origin of manufacture:  USA
Precision:   Integrated circuits:  MBM27C64
Program steps:   Courtesy of:  Brian Green

The PLOT DEMO Solid State Software Cartridge (SSSC) was developed by Texas Instruments for its CC-40 Compact Computer System.

This early prototype of the PLOT DEMO SSSC uses a different form factor and electrical connector than the final cartridges like the SS-3008 STATISTICS SSSC and fits only with the never released prototypes of the Compact Computer 40.

Dismantling this Solid State Software Cartridge manufactured in October 1982 by Texas Instruments reveals a small printed circuit board (PCB) with a MBM27C64 EPROM (Erasable Programmable Read-Only Memory) manufactured by Fujitsu, Japan and programed on January 4, 1983.

The MBM27C64 EPROM uses a CMOS process resulting in a very low power consumption of 40 mW per MHz (or about 12 mW with the slow access of the CC-40) and features a capacity of 8k Bytes with an access time of 300 ns. The Hitachi HN61256P Mask ROM used with the final design of Solid State Software Cartridges for the CC-40 features a higher capacity of 32k Bytes with yet a lower power consumption of 7,5 mW but significantly longer access time of 3.5 us.

Main difference between the two chips is their memory technology. In Mask ROM, the data is physically encoded in the circuit, so it can only be programmed during fabrication. While Mask ROM are very economical in large quantities, there are some major disadvantages associated with the technology: The turnaround time between completing the data set for a Mask ROM and receiving the finished product is long and bugs lead to a long cycle time.

Subsequent developments addressed these problems and the invention of EPROM solved them, because the memory content can be reset by exposure the silicon chip through a glass window in the housing to strong UV light and easily re-programmed.

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Joerg Woerner, December 27, 2020. No reprints without written permission.