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VFP Display Aliasing

Because of the way Win95 switches tasks, when the Run box is checked and the Execute menu's Chunky option is checked, some register displays may not behave as expected. What is happening is that the emulator is running many instructions before the system can update the display, and the register(s) can appear to be static, unchanging. They're changing and being updated, it's just that they're back to the same state that they were when they were last refreshed on the display. Remember that the emulator is going much faster than the display can follow. Unlike an analog display system, which can follow such changes (and shows them as a blur, usually), the VFP regularly "samples" the registers and so displays a clear, if non-intuitive, value. Also, the updates always occur at integer multiples of instruction executions; that has the effect of making the displays "alias" against the operating rate of various instruction loops.

The faster your computer and its associated display hardware is, the more useful the VFP is during RUN.

You can de-select the Chunky option and the emulator will run one instruction at a time, instead of the large batches it normally does. This has two effects; one, it provides more of a timing window for the display to update, and two, it slows down the emulator to a very noticeable degree. Sometimes you'll want to do this, especially when involved in software development.

You can also single step the emulator, which will result in the expected correct register displays.


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