Re: homebrew computer - where to start?


<racter@xxxxxxxxx> schreef in bericht
news:1125732804.697587.191090@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> hi,
>
> i've been a dedicated computer nerd for about twelve years now. i
> started with a cast-off tandy "laptop" that ran BASIC and have been
> hacking ever since, through 386/486/pentium/etc.
>
> now i find myself much more interested in computer systems that appear
> historically before my introduction to computers, and i'd really like
> to get to know these older computing methodologies more intimately.
> i'd like to try to build a computer from scratch - build my own
> processor, etc. - to gain a greater familiarity with the underlying
> technology.
>
> so where do i start? poking around on the internet, all i can seem to
> find is vendors trying to sell "homebrew" computer parts which
> basically involves piecing together readymade components.
>
> i know that the definition of "computer" covers a pretty wide continuum
> right now, but what i'm interested in building is just the basic
> machine: an electronic device that runs programs, whether it has a
> display, printer, or just an array of LEDs as its output.
>
> maybe someone knows a book or something that covers this material.
>
> thanks for your time!
>
> best,
> jake
>


Well, Jake,

A starting point is a matter of choice. Some early calculating machines used
cogwheels and functioned pure mechanicaly. The first electronic computers
used electron tubes by the dozens and required more power then your mains
connection can provide. The first computer I worked on was build with
discrete transistors, ferrite cores and lots of wire all packed in five 19"
rack enclosures higher then a mans length. The first one I build for myself
has a Z80 processor on 4MHz, 2k of RAM and 2k of EPROM. The latter contained
a monitor program derived from the NASCOM. I build, also from scratch, a
separate I/O card for it containing a UART that communicated with a dumb
terminal. The next step was an I/O card that could write to - and read from
cassette tape. Still works when I hook up a PC running a terminal emulator.
At about the same time you could buy Apples or one of its clones. You could
buy an empty board and fill it with components. Some time later you could
buy empty PC- and peripheral boards to do the same. AFAIK the last computer
building that required soldering. These days you can assemble your own
machine even without a screwdriver. IMHO you can't go back but to the first
microprocessors like the 8085, Z80, 6800, 6502 and some others I don't know
well. Some stuff, like the Z80, is still available. Don't know about the
others. Nevertheless, I don't think this is the way to go. The old times
will not come back you know. I advise to look around in the world of
microcontrollers. They have processor, RAM, ROM and I/O in one package but
fiddling with the bits, assembler programming and even soldering are still
required. There is a wide range of them from six pins SOT-23 to forty and
more pins DIP all with eight bits processors. The latter at least as
powerfull as the old Z80 and its contemporaries. If you want more there are
much more powerfull sixteen bits micros available as well. You'll find more
info then you ever can read on the web but you still can do plenty of things
others have not done before.

petrus bitbyter


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