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The Magic of Buzbee

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Build A Computer From Scratch?

Have you ever made a crystal radio? What a fantastic way to learn about the seemingly mystical science of radio waves. Those who are fortunate enough to have tinkered with such devices know first hand the thrill you get from turning a hand-full of specialized components into a functioning device capable of receiving broadcast signals. The successful completion of a relatively simple project such as a crystal radio has the power to transform the hobbyist. At the very least he/she comes away with new insights about radios (of course,) but also - by extension - televisions. In fact one begins to look at all electrical/electronic devices as creations that with enough patience and research the mysteries they hold are within the grasp of those with the desire to understand.
A galena cat's-whisker detector, an early radio wave detector used in crystal radio receivers from about 1905 to the 1940s. The fine metal wire attached to the adjustable arm touches the face of a natural semiconducting crystal of galena (lead sulfide) in the capsule at right. The contact forms a PN junction making a crude semiconductor diode. In a crystal radio its function is to rectify the alternating current radio signal, extracting the audio (sound) signal from the radio frequency carrier wave. Only certain sites on the crystal surface function as rectifying junctions, so the device had to be adjusted before each use by dragging the wire across the crystal to find a "sweet spot".

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CatWhisker.jpg
(http://en.wikipedia.org/wiki/File:CatWhisker.jpg)
My crystal radio fascination is still alive and well in me and as I ponder the hobby I can predict a future post on the subject. For now however, this discussion has been presented simply to strike a chord with those of like mind.

The purpose of this article is to introduce you to a man and his machine. The Man: Bill Buzbee. Journalist turned Computer Scientist. This is a guy who looked at a blinking cursor on a computer monitor and decided that he could do that! This fellow not only built a computer from scratch from hardware to software. But the journalist in him has documented the project with exquisite detail. The Machine: Magic-1. All I can say is Wow! Come on, follow me into the incredible world of "Magic"... [ READ MORE... ]

The following is reprinted from http://www.homebrewcpu.com/

Magic

In the summer of 1980 I celebrated my freshly minted B.S. in Journalism by blowing most of the cash I collected in graduation gifts on a TRS-80 Model 1 computer.  Sitting on the floor of my apartment I fired it up, typed in the sample BASIC program and then "RUN".

WHAT IS YOUR NAME?

"BILL", I responded.

HI BILL

>_

Wow!  I was blown away.  This was just a machine, but I could interact with it using language that we both understood.  As a Liberal Arts graduate with next to no technical background, I found this completely astonishing.  Over the next year, I continued to play with my TRS-80 Model 1 while working as a journalist on a small-town Kansas newspaper.  I decided that I really wanted to learn more about how computers worked, so I went back to college and picked up a M.S. in Computer Science.


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More than 20 years later, I found myself with an urge to touch that magic again by building my own computer from scratch.  By "scratch", I meant designing my own instruction set, wire-wrapping a CPU out of a pile of 74 series TTL devices and writing (or porting) my own assembler, compiler, linker, text editor and operating system.


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I'm calling this computer the "Magic-1", or M-1 for short.  It's a one-address, microprogrammed machine with  one-byte opcodes.  It features 8/16-bit data operations, functioning on an 8-bit wide data bus with 16-bit addresses (mapped via 2K-byte pages into a 22-bit physical address space).   Code and data address spaces can be shared or disjoint, giving each process up to 128K bytes of addressing.   User and supervisor modes exist, along with hardware address translation, memory-mapped IO, and support for DMA and externally-generated interrupts.  As far as components go, it is built entirely out of 74LS and 74F-series TTL devices plus modern SRAM and EPROMs for the microcode store.   After redesigning the memory access mechanism several years into the project, Magic-1 runs at 4.09 Mhz.


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telnet://magic-1.org - Username: guest - Password: magic
Bill Buzbee has graciously opened Magic-1 to the world.
Access is available via telnet at magic-1.org [ Login: guest Password: magic ]. You say you don't telnet? Meet Magic-1 personally, right now at http://Magic-1.org, a website served up by M-1 himself (herself? which is it Bill?) -

I sure hope you contemplate the magnitude of this wonderful adventure Mr. Buzbee has provided. Enjoy!

Coming Soon - Fun With Magic (or, I'm in... now what!)
stay tuned...
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