---
title: "Drawing Apple MEGA-II Breakout in KiCad"
description: "There is a project that has been sitting on my \"to do\" list for too long. My lab notebook has several dedicated pages for it. But I have not made progress. I decided to take…"
canonical: "https://www.baldengineer.com/drawing-apple-mega-ii-breakout-in-kicad.html"
author: "James Lewis"
date: "2018-11-01T13:00:30Z"
lastmod: "2022-04-01T23:43:12Z"
image: "https://www.baldengineer.com/wp-content/uploads/2018/10/Mega-II-Partial-Symbol.jpg"
categories: ["golden-delicious","kicad","projects"]
tags: []
---

# Drawing Apple MEGA-II Breakout in KiCad


There is a project that has been sitting on my "to do" list for too long. My lab notebook has several dedicated pages for it. But I have not made progress. I decided to take some advice I have given to other people. When you're stuck on starting a task, break down the project until you find a piece small enough you can get it done with no problem.

The project involves [the Apple IIgs](https://apple2history.org/history/ah10/). It was Apple's last 16-bit (and 8-bit) computer. Inside are some application specific integrated circuits or ASICs that make the IIgs. The name with my attention is named "MEGA-II." It takes all of the individual logic chips from the original Apple II design and incorporates them into a single 84-pin PLCC.

[![MegaII from AppleLogic 960px](/wp-content/uploads/2018/10/MegaII-from-AppleLogic-960px.jpg)](/wp-content/uploads/2018/10/MegaII-from-AppleLogic-960px.jpg)

Image from [Applelogic.org](http://www.applelogic.org) ([Full](http://www.applelogic.org/files/344S0047loc.jpg))


I need to design some printed circuit boards combining the MEGA-II and a couple of other chips. My current step is creating a library of custom components in [KiCad](http://kicad.org).

With the help of this [Apple II ASIC listing](http://www.applelogic.org/APPLEASICs.html) and a few other resources, my project will capture the entire IIgs schematic. Of course, by the time I finish, someone will have made a python-vision script to convert these scanned schematics to KiCad automatically.

In the spirit of sharing, I streamed part of my schematic capture process. I started with a break out board for my custom MEGA-II symbol. During the stream, I realized the chip I was working with was a PLCC style. There are sockets for this package type. That realization led me to find that I could buy [PLCC break out boards](http://www.proto-advantage.com/store/product_info.php?products_id=2610006). Why re-invent the wheel? Also, using sockets means I can prototype with fewer MEGA-II chips. Using fewer chips means cannibalizing fewer computers.

Getting as far as I did was not a waste. Since I plan to re-create the entire schematic anyway, I can use what I made already. Also, eventually I will add other ASICs to that initial board.

## What is the Apple IIgs MEGA-II Chip?

In this clip, I explain that the Apple IIgs included backward compatibility with the earlier 8-bit Apple-II line of computers. Apple's engineers combined all of the individual logic chips that make up an Apple-II and put them into a custom ASIC. If I add a 6502 processor, some RAM, and an Apple II ROM, I have the basics of an Apple II computer.

[Watch Highlight: Introducing the Apple IIgs's Mega-II chip from baldEngineer on www.twitch.tv](https://www.twitch.tv/videos/328780740?tt_content=text_link&tt_medium=vod_embed)

## Related: Realizing the socket

At this point in the stream, I realized I could socket the chip. Up until this point, I assumed I would need be soldering the ASIC to a breakout board. As I said earlier, sockets are going to save me chips (and time.)

[Watch Highlight: Realizing the MEGA-II should be socketed. from baldEngineer on www.twitch.tv](https://www.twitch.tv/videos/328787221?tt_content=text_link&tt_medium=vod_embed)

## What is the project?

You might be wondering what project I have in mind. I will leave that open for the moment. I do have an end goal with these special chips in mind. But I'm not ready to say what just yet.