Emulator time scale.

I want to get an idea of how the emulated CPU should work when displaying a video frame. Let's see. I know that a frame is drawn every 16625.8 µs. Each frame is composed of 342 lines in the Vertical Active Area and 28 lines in the Vertical Blank Area, for a total of 370 lines. ChatGPT didn't tell me the length of a scanline, but doing some math, 16625.8 µs (frames) / 370 (lines) = 44.395 µs. This length should include the Horizontal Active Area...

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CRT still rules.

In older systems equipped with a video or TV output, it was mandatory to synchronize the times of display of the video image and its composition in the system memory.  The cathode ray, continuously driven by the monitor circuits, lights up dots of fluorescent substance deposited inside the screen. Let's compare this cathode ray to a laser ray, let's imagine moving it from left to right (horizontal active area), turning it on and off at regular...

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Getting the best basis of knowledge.

After a few days of searching for information about the video signal generated by the Macintosh 128K, I found a PDF of a book about this computer, aimed at developers.Actually, I have found several books, but only this one showed me the complete timings of a video frame generated by the Macintosh.This book is what I need for my adventure into coding this emulator. On page 25 of the PDF, in the section "III-18 Over-view of the Hardware", I have found...

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The concept of the "main cycle" of the emulator.

The basic concept behind the emulator is to mimic the functions of the older computer's hardware components. This doesn't mean it replicates the exact hardware physically. Instead, it simulates the behavior of the hardware using software. It can emulate the function of processors, memory, graphics units, I/O systems, etc. Since the hardware components run in parallel, the emulator must run a small portion of the code and update the simulation of...

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The Motorola 68000: Introduction.

Another day, another step forward.The most important thing is not to stop. Anyway, it's better to think about something fun, so I am going to have an overall description of the Motorola 68000.Then, I will dive in to the different aspects of the CPU. My emulator will start from a very small and simple virtual machine made of CPU, ROM and RAM.I would like to start writing a small test virtual machine made of a basic 68k, and expand it little by little. ...

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Getting an overall idea.

Well, before we get into the architecture of the 68k, can you tell me which computers from the past were designed with this CPU? The Motorola 68000 CPU, often abbreviated as 68k, has been one of the most influential in several generations of computers, not just the original Macintosh. Here are some of the best-known computers that used the Motorola 68000 processor family: Apple Macintosh: The original...

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Taking advantage of everything that can help me.

The biggest advantage of having a partner like an AI assistant is that you can work whenever you want without being sent to hell. This is great because while you're working on one or more chats you can stop and continue at your convenience, like I'm doing right now. A new day is starting, I've done the exercises and now I'm resting on the sofa. What a great time to talk to "Jarvis" and move forward with my project. I'll have to come up with...

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How Artificial Intelligence can help me now.

For this project, I need special help. My health issues have changed since the Apple 1 replica project. The learning and studying process can be significantly slowed down. The discouragement, illness, and tiredness caused by a difficult health situation make the development path of a project very difficult if not impossible. I have always fought, this time I want to have a tool at my side that speeds up the process of searching for information and...

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A Macintosh replica to rise the bar.

Today is a new day. I have a new goal, something that will keep my mind busy, and this time I will try to use the help of artificial intelligence. Hopefully, I will be able to overcome some limitations and speed up the making of this project. But, what kind of project is this? You probably already saw a picture that suggests something. Have you seen a Macintosh old computer? Yes, you have! I have the ambitious goal to build my own Macintosh 128K...

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When needs meet Artificial Intelligence: the beginning.

I have decided to start a new project. I need to set myself a short/medium-term goal to keep me busy. My life will soon take a toll on me and having an exciting project to distract me is vital. In the past I have tackled projects involving retrocomputers, a topic that I particularly love, so I revisited an idea I had some time ago, after I built a replica of the Apple 1 computer at the Embedded World 2019 fair, in Nuremberg, Germany. Four years...

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