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Thread: Which CP/M for a new port: 2.2 or 3?

  1. #51
    Join Date
    Jan 2007
    Pacific Northwest, USA
    Blog Entries


    That's standard behavior for the entire x80/x86 crowd. In fact, where you have prioritized interrupts (i.e. you have an interrupt controller), it's good practice to enable interrupts as early as possible in your ISR, so that higher-priority interrupts can be serviced promptly.

    As an example, suppose you're using an Intel 8275 CRT controller connected to an 8257 DMA controller, not operated in "auto-initialize" mode (sometimes you need all of the DMA channels). The CRT DMA servicer is high priority to keep the display going and lower priority ISRs should enable interrupts as quickly as possible so that the display doesn't flicker.

  2. #52
    Join Date
    Feb 2017
    Zürich, Switzerland


    @ChuckG: in this case, though, they're disabling interrupts at the top of the ISR...

    Anyway, I made a video with the NC200 in it, if you want to see it in action. Sadly, my microphone didn't pick up the floppy disk noise.


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