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User:Larz: Difference between revisions
From London Hackspace Wiki
→TRS-80 (Z-80)
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In 1978, the TRS-80 only displayed upper case characters. This was done to save one chip. With only 7 RAM chips in the video circuit, the system was limited to displaying the first 128 characters of the character ROM. | In 1978, the TRS-80 only displayed upper case characters. This was done to save one chip. With only 7 RAM chips in the video circuit, the system was limited to displaying the first 128 characters of the character ROM. | ||
I piggy-backed a 1K x 1 ram chip (that's 1024 bits - 2021A) onto the character generator circuit to allow all 8 bits of the character ROM to be accessed. A toggle switch on the side of the case let you turn the mod on and off. Not bad considering I was 14 years old and the machine cost $ | I piggy-backed a 1K x 1 ram chip (that's 1024 bits - 2021A) onto the character generator circuit to allow all 8 bits of the character ROM to be accessed. A toggle switch on the side of the case let you turn the mod on and off. Not bad considering I was 14 years old and the machine cost $600. | ||
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