Things were different in the early days. In the 1970's I worked at a company that had an IBM S/370 and a clone, an Itel AS/5. IBM supplied hardware schematics

Things were different in the early days. In the 1970's I worked at a company that had an IBM S/370 and a clone, an Itel AS/5. IBM supplied hardware schematics and microcode listings for their S/370 hardware. They were in the machine room and freely available for perusal by us. In a bit of irony, they also supplied schematics and microcode for the Itel clone. That's because the Itel was a true clone. It was designed by copying IBM's circuitry, but implemented in Motorola 10K series ECL instead of IBM's proprietary technology. You read that right. In order to debug a problem with the Itel, the Itel field service engineers used IBM's schematics. I think a lot of this free availability was because IBM was facing antitrust pressure from the US government. I don't know all the details. Here's more history about the clone: http://www.silogic.com/NAS/NAS.html http://www.silogic.com/NAS/NAS.html