eolas/zk/Williams_Tube_memory.md

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---
tags: [computer-history, memory]
created: Tuesday, September 17, 2024
---
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# Williams Tube memory
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- One of the early attempts to create RAM in computers based on the EDVAC
stored-program architecture.
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- Worked by displaying a grid of dots on a cathode-ray tube ("screen")
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- Due to the way CRTs work, this creates a small charge of static electricity
over each dot. The charge at the location of each of the dots is read by a
thin metal sheet just in front of the display.
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- Each dot position could be written to and read from and the pattern was
constantly refreshed as the dots would fade over time.
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![A Williams CRT tube](../img/williams-tube.jpg)
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![Memory dot pattern from a Williams Tube](../img/williams-tube-dots.jpg)