TeXShopIntel and Arm
I retired from the University of Oregon in 2002, and after that I attended every Apple Developer Conference except one until 2011, the last conference before Steve Jobs died. I missed the 2005 conference because I was teaching a course for a colleague with an emergency. Shortly before that 2005 conference, the Wall Street Journal published a rumor that Apple would switch from the PowerPC to Intel processors at that conference. Switching processors is a massive undertaking and the Wall Street Journal is not a standard Apple site, so most of us dismissed the rumor, but it turned out to be true. Job's keynote address is still available on the internet, and it is one of his masterpieces.
Among other things, that keynote told developers how they could transition their products from PowerPC to Intel. In 2005, most Macintosh programs were written in one of two ways: using Carbon, or using Cocoa. Carbon was based on the old style used when programming the 1984 Macintosh, and many commercial programs used that approach because it was easy to transition from the old Mac to macOS. Cocoa was the object oriented approach inherited from NeXt and not yet used by many commercial products. Jobs stated that Cocoa programs could be transitioned easily, perhaps in less than a week. Carbon programs would require more effort, a month or more of solid work. Jobs announced that developers could rent an Intel Macintosh from Apple to help with the transition. Of course I ordered one of these machines. It arrived two weeks after the conference ended.
TeXShop is written in Cocoa. Writing a front end with the old Carbon was a very difficult job, but Cocoa provided an editing window and a pdf display window for free and made the job incredibly easier. Within two days of receiving the rented Intel machine, I had an Intel version of TeXShop, working just as well as the original PowerPC version.
Jumping ahead a decade, in June of 2020 Apple announced a transition of their computers from the Intel processor to the Arm processor. Once more, they offered developers a rental Arm machine to help with the transition. Mine arrived two weeks after WWDC. Within a couple of days, I had a fully functional Arm version of TeXShop. Then I turned to MacTeX and the TeX binaries in this distribution. Most compiled on Arm without issue, and after a week I had a universal version of the binaries, each with an Intel and an Arm version of the code. Apple first released Arm machines in January of 2021, and on the first day we made available a universal TeXShop and universal TeX binaries.
TeX Live is officially released once a year, around April, so for several months users could use universal Intel/Arm binaries, housed in a binary directory named x86_64-darwin. Then the 2021 version of TeX Live and MacTeX was released and the name of the binary directory became universal-darwin.
Both of these transitions were carefully planned in advance by Apple, but I'm still astonished how easily each was accomplished. And each transition was crucial. In his keynote address, Jobs clearly explained the reason for the PowerPC/Intel switch: in a nutshell, the switch made it possible to create powerful portables that did not heat up or exhaust the batteries. The Intel/Arm switch was even more astonishing to me, because those original rental Arm machines were essential equivalent to older Intel machines, but the actual production Arm machines turned out to be incredibly faster and at the same time incredibly more power-efficient than their Intel counterparts.