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The partnership between IBM and Motorola is something I find intriguing. And I'm not just talking about PowerPC. In the 80s -- long before Hercules -- IBM devel

The partnership between IBM and Motorola is something I find intriguing. And I'm not just talking about PowerPC. In the 80s -- long before Hercules -- IBM developed a "mainframe on a card" solution for use in IBM PCs. For a CPU, they commissioned Motorola to build a special 68000 CPU with different microcode that implemented a large subset of the System/370 instruction set. Any instructions that could not be implemented with this custom-schmustom architecture would trap, and be decoded and emulated by a regular 68000 that ran in tandem with the custom one. The resulting architecture was able to run mainframe operating systems and applications very well, providing mainframe developers a benchside testing solution that allowed them to run software still in development without tying up resources on the actual mainframe (which needed to have as much CPU time as possible committed to production workloads in order to be profitable to run). Still probably cost an arm and a leg, though. The cards weren't sold on their own, but installed inside a PC under the names Personal Computer XT/370 or AT/370: https://en.wikipedia.org/wiki/PC-based_IBM_mainframe-compatible_systems#Personal_Computer_XT/370 https://en.wikipedia.org/wiki/PC-based_IBM_mainframe-compati...

sillywalk 2y ago
I remember reading about that, from the Chipletter in 2022[0]: "The XT/370, with a hard drive, could be purchased for as little as $8085. This compares with a basic PC/XT with 256K RAM for $4395 and adds a lot more functionality." ... "So what was the PC XT/370? Put simply, it was a PC XT (the original IBM PC with a hard disk drive) with three additional cards: PC/370-P : A card with one modified 68000, one standard 68000 and lots of logic chips. PC/370-M : A card with 512 kilobytes of memory. PC/370 EM: Providing the ability to emulate an IBM 3270 terminal. The XT/370 then became three machines in one: An IBM PC/XT. An IBM 3270 terminal that could be used to access a System/370 mainframe. A machine capable of running some System/370 software." [0] https://thechipletter.substack.com/p/motorola-intel-ibm-make-a-mainframe https://thechipletter.substack.com/p/motorola-intel-ibm-make...

sillywalk 2y ago

I remember reading about that, from the Chipletter in 2022[0]: "The XT/370, with a hard drive, could be purchased for as little as $8085. This compares with a basic PC/XT with 256K RAM for $4395 and adds a lot more functionality." ... "So what was the PC XT/370? Put simply, it was a PC XT (the original IBM PC with a hard disk drive) with three additional cards: PC/370-P : A card with one modified 68000, one standard 68000 and lots of logic chips. PC/370-M : A card with 512 kilobytes of memory. PC/370 EM: Providing the ability to emulate an IBM 3270 terminal. The XT/370 then became three machines in one: An IBM PC/XT. An IBM 3270 terminal that could be used to access a System/370 mainframe. A machine capable of running some System/370 software." [0] https://thechipletter.substack.com/p/motorola-intel-ibm-make-a-mainframe https://thechipletter.substack.com/p/motorola-intel-ibm-make...