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The Complete Bus Logic of the Intel 8088

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In a previous article , I described a simple state machine to explain the prefetch behavior and miscellaneous observed bus delays of the Intel 8088. I now believe that the model I described there - although successful in modelling the 8088's behavior - was unnecessarily complex. There are in fact far fewer legitimate bus "delays", and they do not relate to internal state transitions. I have also slightly revised my description of the BIU's prefetching logic - I now believe that the prefetching decision happens at the end of T2, instead of the beginning of T3. There may not be much of a distinction between the end of one cycle and the beginning of the next, but it lines up better in our new diagrams. Introduction If you were interested enough to click on this article, you are probably already familiar with the 8088's bus cycle timings. A single bus cycle on the 8088 takes a minimum of 4 CPU cycles, consisting of 4 T-states numbered T1, T2, T3 and T4. Wait states (T
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Bus Sniffing the IBM 5150: Part 2: Writing a 8088 sigrok Decoder

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In my last article , I dodged the issue of writing a custom decoder for the 5150's bus signals to use in DSView, instead just processing the exported CSV with the pandas Python library.    This had the advantage of familiarity, but we're leaving some powerful tools on the table. Turning Excel into a logic analyzer display may be a cute trick, but it comes with a few limitations. Zooming out and scrolling is a bit awkward and slow, and of course, there's that 1M row limit staring us in the face. Ultimately, our goal is to eventually compare execution results between our logic analyzer and our emulator. How are we going to accomplish that? A simple CSV diff goes off the rails the moment an interrupt occurs at a different time, even though that timing difference may or may not represent an accuracy problem. Diffing cycle logs is no trivial task. In contrast, a competent logic analyzer program scrolls through massive numbers of samples and zooms in and out with ease. What's
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