TRS-80 Model 4 (1984)

Radio Shack released the TRS-80 Model 4 as a follow-up to the Model III three years later in 1983. It looked essentially the same as the Model III except that it was an off-white color instead of grey/silver. Internally, there were some fairly significant upgrades, including:

• CPU: Z80A @ 4 MHz (compared to the ~2 MHz model III)
• Display: 80x24 (compared to the 64 columns of the Model III)
• Available 64KB model (Upgradeable to 128KB of RAM)

It also included an expanded keyboard and TRSDOS 6. For this version of TRSDOS, Radio Shack contracted with the maker of LS-DOS/LDOS, a popular and generally more capable 3rd party DOS produced for the TRS-80 line. They continued to market LS-DOS separately but it and TRSDOS were now essentially the same.

The following configurations were available:

• A diskless version with 16KB RAM (cassette only): $999</li
• A single disk version (180K single sided, double density) with 64KB RAM: $1699
• A dual disk version with 64KB RAM: $1999

The Model 4 was the last major revision the the TRS-80 line though there would be a somewhat enhanced Model 4D released in 1985 that would be sold through at least 1991.

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