Comment by LeoPanthera
3 hours ago
The UK did not have emissions regulations at the time, and the most popular computer of the early 80s in the UK, the Acorn BBC Micro, had no shielding whatsoever.
Acorn wanted to break into the US market, and so they had to redesign the computer with a massive metal box inside the outer plastic case.
Their attempt to launch in the US was a huge failure, and most of those computers were shipped back to the UK and "unconverted" to be resold in their home market.
But they didn't remove the metal box. So Brits could always tell when they had an ex-US BBC Micro because it weighed twice as much and had a huge metal box inside it.
Seems strange no one came up with spraying the inside of the case with a metallic shielding layer of paint, as some later products eventually did.
Author of the OP here. The "spray" technique was known in the early 80s, if not earlier. It's mentioned in Michael Tomczyk's "Home Computer Wars":
> The solution came in several forms. One way was to embed ferrite balls in the plastic case. Another way was to spray the inside of the case with a metal coating. But the best way was to encase the offending electronics in a small metal box inside the case, which is what was done with the VIC-20. [0]
Why a metal box is the best way, he doesn't say and I don't know. My best guess is that it was more effective/reliable at passing the tests.
[0]: https://archive.org/details/the-home-computer-wars/page/205/...