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Not even the weirdest thing IBM did to get compatibility between their mainframes and other CPU architectures. To build the XT/370 and AT/370 expansion cards, t
by bitwize 1mo ago
Not even the weirdest thing IBM did to get compatibility between their mainframes and other CPU architectures. To build the XT/370 and AT/370 expansion cards, they custom-ordered modified 68000s that decoded System/370 instructions instead of the 68k instruction set, with most of the instructions handled by the new microcode and the few stragglers software-emulated:
https://en.wikipedia.org/w/index.php?title=PC-based_IBM_mainframe-compatible_systems#Personal_Computer_XT/370 https://en.wikipedia.org/w/index.php?title=PC-based_IBM_main...
- sillywalk 1mo agoA couple more articles on them. https://thechipletter.substack.com/p/motorola-intel-ibm-make-a-mainframe https://thechipletter.substack.com/p/motorola-intel-ibm-make... https://www.cpushack.com/2013/03/22/cpu-of-the-day-ibm-micro-370/ https://www.cpushack.com/2013/03/22/cpu-of-the-day-ibm-micro...