Model and ROM information

Information regarding Model type, PCB code, ROM marking, ROM version and checksum is captured here. S. Adolph

  Note: I'll try to keep this list updated.  If anyone has comments or corrections to this please let me know.

What Kind of Model 100 or Tandy 102 do You Have?

Model 100

The first M100s were released with a custom ROM pinout, in agreement with the published schematic. Over time, Radio Shack changed the design to use standard 27C256 compable ROMs. Both variants use essentially the same ROM code. Clearly the schematic for these later variants was different due to the ROM pinout.

Later, versions of the M100 were produced for UK and EU markets. These M100 appear to use 27C256 compatible ROMs, but the ROM code differs from the USA version. The schematic for these versions had changes as the UK M100 had no modem function, and the EU version had a different modem.

Tandy 102

Tandy introduced the 102 from the beginning using a 23C256 compatible ROM. There is a published schematic available. the T102 main ROM had a few improvements and bug fixes compared to the standard M100 main ROM.

Later, versions of the T102 were produced for UK and EU markets. The ROM code again differs from the USA version.

You can tell these variants apart by observing the presence of the modem, and by looking at the PCB itself. The ROMs will have a unique marking, as does the PCB. In some cases the Tandy product number is different as well. This information is captured in the below table.

Board Code ROM type ROM Code Comment

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PLX110CH1X custom LH535618 early North America PLX110EH1X 27C256 compatible 3256C07-3J1 late North America PLX120CH1X 27C256 compatible 3256C05-3E1 European/Italian