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Virtual Machines

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Originally published in Queue vol. 2, no. 5
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Comments

(newest first)

Michael Rieschl | Thu, 20 Dec 2012 17:01:45 UTC

One of the earliest simulators is the OS 2200 Fault Location by Interpretive Testing (FLIT) product. FLIT has been used by Univac / Sperry / Unisys to simulate an entire OS 2200 environment. The instruction processors are emulated as a register-to-register simulator. The instruction processors, control units, and devices are packet emulators. The tape media are files in FLITs TTF format and the disk media are files in FLITs DTF format.

FLIT has been used to emulate all of the 2200 computer systems prior to development. In our older CMOS systems this was extremely important because waiting for the chips to be designed and waiting for test systems would delay software development. Using FLIT the operating system and associated software could be tested and debugged while the hardware was being developed.

FLIT executes in system mode as described above, but also executes in program mode which is the instruction processor emulator with an emulated 2200 operating system. Program mode is used to load and test 2200 programs.

Additionally FLIT has a post mortem dump mode for program mode and a panic dump mode for system mode. All 2200 panic dumps are processed by loaded into FLIT and are processed by FLIT panic dump functions.

-Mike


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