30 Jul
2007
30 Jul
'07
4:17 p.m.
Thanks for your advice, Tony. To address question #1, I'm honestly not too
sure. I figure ha wih the early micros, there is documentation, where as
something completely homebrew, there is little, if any. What I need to find
is a good resource for electronic circuit design. I have a book called "How
to Build Your Own Working Microcomputer" that I bought for under a dollar at
a thrift store. I still need to finish it, but it doesn't seem to be much
help in that respect.
As for your second question, I would find it to be really fascinating to
build a computer out of TTL, but again, I need some kind of resource to
guide me through it. All my knowledge on electronic circuitry is very basic
right now. My father, an electrical engineer, tells be that he couldn't
even do it after six years of college(although, he graduated 20 years ago),
so I'm not very hopeful that I could.
Third, commercial software would be nice, but I don't need it. I would very
much like to learn machine code. I figure that when I start college
interviews in a year going toward something in the technology field, I'd
like to have as much pre-knowledge of computer science as I can. I figure
that there's no better way than to build and program a computer. It will
take me a long time, but it would be worth it.
In addition to my trusty Weller Iron, I do have an old Hitachi Oscilloscope
and a Hewlett Packard Digital Multimeter. If absolutely necessary, I could
try and find a logic analyzer, but thats one of those things I don't quite
have the money for.
Finally, I would most definitely use chip sockets. I don't want to risk heat
damage to components if I can just solder in sockets and install the actual
ICs later. It may not be as good for reliability, but it is better for ease
of design and construction
On 7/30/07, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Hello, everyone. My name is Joe, I am 17 years old, and live in central
NJ.
I would like to figure out how to build a
retro-type computer, either
from
plans or from a kit. I am currently considering
the Micro-KIM, as well
as
trying to build a mark-8. Not sure what I want to
do. If anyone can help
me
along with this, I would be very appreciative.
I think the first thing for you to do is to work out what you want to do,
or what you want the computer to do.
A few thoughts.
1) Do you want to make a clone of one of the well-known early-ish micros?
2) Do you even want to make a microcomputer at all, or would you like to
make your own process for gates and flip-flops (it doesn't that _that_
many chip,s I think it can be done in under 100 TTL packages)?
3) Do you want to run commeraical (of 30 years ago :-)) software, or will
you be happy with a mcachine code monitor and entering your own little
programs on toggle switchss or a hex keypad?
Others have mentioned the need for a good soldering iron. I'll go along
with that (I use an old Weller). But actually, the good ireon is more
important for taking things off the PCB (when you make a mistake) without
damaging the PCB. In general you can solder the PCB with just about any
iron.
What about test equipment? Particularly if you design your own machine,
or work from just a shcematic, it is _not_ going to work properly first
time (that is the voice of experience, I can assure you). You will have
to debug it. Now I debugged my first homebrew computer (Z80 based) using
nothing more than an analogue multimeter (VOM) and an LED+resistor to
look at logic states. I don't recomend it!. A 'scope is very useful, so
is a logic analyser.
One final point. Much has been said in the past about unreliabiltiy
caused by IC sockets. This may well be an issue for commercial boards,
but for homebrew prototypes (as you are considering building), I would
recomend using turned=pin DIL sockets for _everything_ unless there's a
good electrical reason (stray capacistance or inductance, for example)
for not doing. Having ICs in sockets makes debugging a lot easier.
-tony