Texas Instruments 8K EPROM EXPANSION Cartridge

Date of introduction:  Never
 (Announced: 1983)
Display technology:  
New price:   Display size:  
Size:  2.1" x 2.0" x 0.55"
 53 x 52 x 14 mm3
Weight:  1.2 ounces, 32 grams Serial No:  0063032
Batteries:  n.a. Date of manufacture:  wk 11 year 1984
AC-Adapter:   Origin of manufacture:  USA (LTA)
Precision:   Integrated circuits:  MBM27C64
Program steps:   Courtesy of:  Joerg Woerner

The 8K EPROM EXPANSION Cartridge was developed by Texas Instruments for its CC-40 Compact Computer System and increases its power and versatility by increasing the Read-Only Memory (ROM) capacity of the computer. The additional memory provided by the 8K EPROM cartridge can be used to expand the total amount of memory available for BASIC programs and constant data storage, or to increase the amount of memory available for machine language programs.

Read-Only Memory (usually known by its acronym, ROM) is used in computers and other electronic devices to store programs and constant data. 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, or Erasable Programmable Read-Only Memory, solved the problems, because the memory contend can be reset by exposure the silicon chip through a glass window in the housing to strong UV light. The same EPROM chip packaged into an opaque housing, results in the OTP-ROM, or One-time Programmable Read-Only Memory, a technology usually used for quick production ramp-up at higher costs. The development of the Flash Memory, a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory), allows changes in the programs or data on the fly and replaced mask ROM in most applications.

Dismantling this 8K EPROM EXPANSION Cartridge manufactured in March 1984 by Texas Instruments in their Lubbock, Texas facility, reveals a small printed circuit board (PCB) with one MBM27C64 EPROM (UV Erasable and Electrically Programmable Read-Only Memory) manufactured by Fujitsu, Japan. The Cartridge has a small removable lid exposing the bare silicon of the EPROM chip to reset it with UV light.

The MBM27C64-30 uses a CMOS process resulting in a very low power standby consumption of 0.55 mW and features a capacity of 8k Bytes with an access time of just 300 ns.

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Joerg Woerner, October 20, 2019. No reprints without written permission.