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The Grid Compass, released in 1982, was arguably the world's first full-fledged laptop, whose only glaring deficiency to modern eyes is the small display, 320x240 with physical size to match, something that would have significantly restricted its usefulness in a world of desktops with 80-column text. (Compare to the otherwise similar Toshiba T3100, four years later.)

Obviously a larger display would have cost more, but intuitively, the benefit would have been easily worth the cost. Where does intuition go wrong? What was the obstacle with a larger display that was so severe that it led to the designers settling for 320x240?

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    Well, the compass did 80x24 at that resolution, and 80-column in 1982 was still not super-common. The new IBM-PC had it, the Kaypro II had it, and the PET 8000-series had it, but most contemporary machines of the day had far less. I'd venture a guess that some element of the electroluminescent display used on the Grid Compass - whether it was cost, heat dissipation, or something else - was a factor in choosing that particular size panel, but that's just conjecture. – Joe May 16 '17 at 20:29
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    As to physical size, it might be yield at a guess. If there's an x% chance of a panel of size q being manufactured without defect then it's x^4% for a screen with twice the diagonal, and each failure costs four times as much in materials and manufacturing. – Tommy May 16 '17 at 20:34
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    Interestingly this says the text resolution was 53x24: books.google.com/… which seems more reasonable with a 6x8 grid. – Joe May 16 '17 at 21:11
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    @Joe Looking at those screenshots, the characters were 4 pixels wide. That's how it's 80 columns maybe. It's surprisingly readable though! – Wilson May 17 '17 at 6:08
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    @Joe - Cost was definitely a factor; I worked for a small company in 1983/4 that sold the GRiD Compass, and the ELD was a major factor in the cost. The quite compact desktop Bytec Hyperion (which the company also sold), with an amber CRT, was more expensive than the Compaq or the IBM PC, and the GRiD was even more expensive than the Hyperion. – Jeff Zeitlin May 17 '17 at 11:40
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I just came across a possible answer at http://www.indiana.edu/~hightech/fpd/papers/ELDs.html

"The most important problem that had to be solved before mass production of ELDs could begin was increasing the reliability of the EL thin film stack. Since the devices operated at very high field levels -- about 1.5 MV/cm -- there was a high probability that they would break down, especially if there was insufficient uniformity in the stack. Sharp, Tektronix, and Lohja Corporation in Finland were able to solve this problem between 1976 and 1983 using slightly different approaches."

That suggests maybe early high-resolution ELDs couldn't be had for any price if you wanted reasonably high reliability too?

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