Just want to add that they're very common on 1980s computers in Britain. Sinclairs and Amstrads have them. And that they often fail and are very hard to replace. Essentially you end up taking one from another machine, so the stock of working machines declines over time.

Ferranti.

Now that is a company that had a wild ride. It could have become the Xilinx instead it ended up with a wild story involving illegal arms exports and other insane stuff.