Apple went to the trouble of designing a switching power supply at a time when they were still quite new and not widely used for consumer electronics, perhaps because Steve Jobs liked the aesthetics of putting the power supply within a plastic case that had a monitor sitting on top, which would have made a fanless computer prone to lethal overheating if it used a linear power supply (that would have generated more heat).

How much did this switching power supply cost, per unit, compared to the linear power supplies used by other manufacturers like Commodore?

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    Here's an interesting article on the subject (but doesn't answer the question): righto.com/2012/02/apple-didnt-revolutionize-power.html – traal Jun 27 '18 at 3:20
  • A “real” cost figure will only be available from Apple... but it was most likely more expensive - given the price of the computer then a reasonable decision - reliability, less heat , less noise etc all came into the decision. – Solar Mike Jun 27 '18 at 8:09
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    Acorn's BBC Micro essentially made the same engineering decision. The BBC specified a linear PSU so that's what went into the early models, but they were so unreliable due to the heat that they eventually also went to switching PSUs. I note that about a third of the board space in the cost-reduced Acorn Electron was a switch-mode PSU, albeit taking 18VAC from an external transformer rather than mains directly, so switch-mode was cheaper than linear by 1984. – pndc Jun 27 '18 at 8:44
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    @traal it does however strongly suggest that if you could get hold of "Switching supplies grow in the bellies of computers", Electronic Business, volume 9, June 1983, p120-126 then you'd get a pretty good answer — that's the source for the claim that Apple's switch of supplier to Astec added $7/unit. – Tommy Jun 27 '18 at 16:05
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    Also via the article linked by traal, a nearly-equivalent contemporaneous power supply from Boschert Associates was available for $199 retail (cf. bitsavers.org/pdf/microcomputerAssociates/… ). So probably a price close to that. – Tommy Jun 27 '18 at 16:10

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