With modern computers and game consoles, it's common to have the ability to take 115 or 230 volt mains supply, selected by a small switch on the back of the machine. Presumably the logistical advantage of not needing separate SKUs for America and Europe, outweighs the cost of some extra circuitry.

When did microcomputers start having this feature?

Edit: I thought there was always a small manual switch. If some machines can do this completely transparently, that counts too!

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    To clarify, are you asking about micros that had a manual switch for this capability? Which may or may not have come before PSUs that supported either input voltage "transparently"... – Brian H Jul 27 '17 at 21:53
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    PSA: be very careful with that little red switch! thedailywtf.com/articles/The-Little-Red-Switch – snips-n-snails Jul 27 '17 at 22:06
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    At least some Apple II power supplies had 115/230 voltage selection switches. You can see a "VOLTAGE SELECTION SWITCH 115/230" listed among the components of an Apple II power supply on page 13 of this Apple document on the Astec power supplies they used in 1982: bitsavers.informatik.uni-stuttgart.de/pdf/apple/power_supply/… You can see a picture of the switch here: tech.markoverholser.com/files/HPIM5335.JPG – Ross Ridge Jul 28 '17 at 1:13
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    I don't believe this has anything to do with computers. The introduction of dual voltage supplies affected TVs, VCRs, CD Players, Fridges, etc, etc. – Chenmunka Jul 28 '17 at 7:14
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    Voltage selection switches were common even in 1950's radios and professional equipment, usually selecting taps on the transformer primary. – rackandboneman Aug 1 '17 at 12:08

It was about when the ATX standard became the norm. Of course, a few late AT power supplies had this feature, but it was a rather niche feature.

Most ATX PSUs have a little, usually red switch that allows end-user to change the voltage accordingly. It's worth mentioning that a few OEMs used do stick something over those switches to avoid users from changing them - less because they wanted to disallow users to move with their computers, more because someone might fiddle with the switch and break the PSU.

Besides desktop power supplies, it's also worth to mention laptop ones; Laptops had power supplies that were able to change voltages automatically a little bit later than ATX power supplies arrived. It was about 1998-2000 that they became a norm, but some chargers like IBM's 85G6733 arrived earlier (about 1996-1997).

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    Wikipedia en.wikipedia.org/wiki/IBM_Personal_Computer_XT says that first power supplies for XT were 120v-only, and international ones were 240v-rated. For most 240v power supplies with half-bridge topology the ability to use 120v comes almost for free -- by switching mains rectifier into voltage multiplier. Therefore, this ability for AT power supplies probably came as soon as ibm pc/xt became international. – lvd Jul 28 '17 at 6:29
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    I have a tub of AT PSUs, and at least 50% of them have the voltage selector switch. I wouldn't say that this is niche at all. The original IBM machines didn't have this, but many of the later clones did, if I recall correctly. – Cody Gray Jul 28 '17 at 12:25
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    Many computer's power supplies way before the ATX standard had this multiple voltage feature. I recall that the Amiga 2000 shipped with one. My first hand experience building many no-name IBM PC clones in the late 80's these types of power supplies were very commonplace. – dmarietta Jan 29 '19 at 20:31
  • Unfortunately I don't have the machine anymore, but I seem to recall that my ITT Xtra (10mhz Turbo XT Clone) had the red switch. That was a mid to late 80's machine. – Brian Knoblauch Jul 22 '19 at 13:45

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