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Building your own computer

Posted: Tue Oct 23, 2012 9:26 am
by wellwisher12
Hello all,

How difficult is it to build your own computer? And how difficult is it to learn it when you do not have any experience? How fast will you be able to learn it?

Re: Building your own computer

Posted: Tue Oct 23, 2012 9:43 am
by RaTTuS
it depends
from what level do you want to build one.... i.e. nan gates and up [not really this forum]
or are you talking about plugging things into a motherboard [not really the idea of this forum]
or are you wanting to plug your RPi into a box ?

Re: Building your own computer

Posted: Tue Oct 23, 2012 9:57 am
by JoeDaStudd
If you mean assembling a desktop computer its very easy.
Think lego only with wires/cables.
As long as you read the motherboard and case manual you can't really go wrong.
Just read up and/or watch a few online guides.
Picking the hardware on the other hand isn't too easy as prices are always changing, parts are always being released and the next best thing is always a few months around the corner.

However if you mean creating a computer like the raspberry pi from scratch then I wouldn't have a clue where to even start.

Re: Building your own computer

Posted: Tue Oct 23, 2012 12:53 pm
by liz
Eben has a fantasy curriculum he talks about occasionally, where on day 1 students would be presented with a lump of germanium, from which they would make a point-contact transistor. On completion of that task, they'd be given a bag of transistors, from which they'd make logic gates. They'd then be given a bag of logic gates, from which they'd make higher level constructs like ALUs, adders and other components of a processor. Etc. etc.

Teachers tend to point and laugh when he mentions this scheme to them.

Re: Building your own computer

Posted: Tue Oct 23, 2012 12:56 pm
by PeterO
Actually you don't need that big a bag of gates. If you look back at the designs of the 1950s and early 1960s machines they didn't have the millions of gates needed for modern designs.

You might also find this interesting : http://www.nand2tetris.org/
"Building a Modern Computer from First Principles"

PeterO

Re: Building your own computer

Posted: Tue Oct 23, 2012 12:59 pm
by jaromanda
liz wrote:Teachers tend to point and laugh when he mentions this scheme to them.
Of course they'd laugh ... what a preposterous idea!!!

50% of the kids would be too busy tweeting about how lame the lesson is
the 40% with diagnosed ADHD would lose interest after 30 seconds
and the teacher would be busy dodging the lumps of "rock" they so generously supplied being thrown at them by the remaining 10%

:D

Re: Building your own computer

Posted: Tue Oct 23, 2012 1:30 pm
by tech_monkey
I actually designed and built a computer. It was part of my HND electronics course work. We where given the specs on an 8 bit processor chip, and told to design a computer using this chip that when booted up would a run a program stored on an eprom. It basically flashed a few LEDs connected to some outputs. Once we had the design we then had to design a PCB and make the thing. The PCB had to be double sided.
Mine and three others worked first time. The rest eventually worked, but it was quite amazing to see 16 different designs for the same thing, even the PCBs where all different. The 4 that worked first time all followed similar design principles. We had all our chips in the same direction ie all pins 1 on the top left. All chips where vertical. all other components where oriented in a similar way so resistor colour codes started either from left to right or top to bottom. This makes fault finding easy and you can see straight away if a chip is inserted upside down. Plus it looks neater.
So to answer the original question, how long is a piece of string. What sort of computer do you want to build. One that runs a single program after power on, one that's more like an R-pi or something a bit more complex.

Re: Building your own computer

Posted: Tue Oct 23, 2012 3:57 pm
by toxibunny
If you want to build your own computer from scratch, you must first create a universe...

Re: Building your own computer

Posted: Tue Oct 23, 2012 4:21 pm
by W. H. Heydt
liz wrote:...they'd be given a bag of transistors, from which they'd make logic gates.
I did that in college. The gates worked fine (TTL), but the flip-flop assembled from the gates didn't.

I also helped one of my kids do a science fair project of a 1-bit adder circuit (including carry out) using relays.

Re: Building your own computer

Posted: Tue Oct 23, 2012 4:35 pm
by jackokring
liz wrote:Eben has a fantasy curriculum he talks about occasionally, where on day 1 students would be presented with a lump of germanium, from which they would make a point-contact transistor. On completion of that task, they'd be given a bag of transistors, from which they'd make logic gates. They'd then be given a bag of logic gates, from which they'd make higher level constructs like ALUs, adders and other components of a processor. Etc. etc.

Teachers tend to point and laugh when he mentions this scheme to them.
How would they ever get to using buried n+ layers, and dielectric film gates? Never mind things like sandwich gate pairs and the DISCO fet, with all the other bits. Also the h(fe) of a point contact transistor is not very high, as the charge carrier density difference between the emitter, base and collector is not very high.

Re: Building your own computer

Posted: Wed Oct 24, 2012 3:02 am
by Jim Manley
Eben, given your track record, if you build it, we will come ...

At the Computer History Museum, we have a duplicate of the very first Bell Labs whisker-hair transistor that Shockley, Bardeen, and Brattain built. When I built my first germanium crystal AM radio, I couldn't believe that it could actually receive and amplify radio signals from scores of miles away, even occasionally over 1,000 miles away in the case of WGN in Chicago, which could be heard from the New York metro area late at night when the ions were cooperative (its 50,000 watts at 720 KHz can sometimes even be heard as far away as South America, Europe, and Australia).

As far as I'm concerned, every kid should build these kinds of devices so that they'll better appreciate how magical it is that their cell phones ever complete a call, much less are then able to occasionally drop one! ;)

Re: Building your own computer

Posted: Wed Oct 24, 2012 3:59 am
by Lob0426
So now we need a BRCM2835 and PoP memory mounted on a pin package. And a LAN9512 on a pinned package. A board that will accept 1812 smd parts, regulators, connectors and such.

A new age Timex/Sinclair ZX81 kit!

Of course a SoC that used a board mounted memory would be better for a kit, at least in my opinion

Re: Building your own computer

Posted: Fri Oct 26, 2012 2:52 pm
by tech_monkey
@ Jim.
Glad I'm not the only one. I built my first crystal set radio when I was about 10. Saw a program on TV about how prisoners in WW2 built crystal sets and then the presenter built one using a germanium diode and a few other things. I can still see the look on my mums face when I asked her for a toilet roll, so I can build a radio. My parents thought I was nuts but there I was wrapping wire around the toilet roll and connecting a diode and a crystal earpiece. Then I heard some music. Wow it worked. I then built a huge aerial in the garden it was actually a modified army field aerial I bought for a quid. Then built an amplifier from a circuit in a mag I saw. The gradually added a few more bits and bobs changed the amp for a better one. I then re did the whole thing using a Gakken Denshi Block system using my own design rather than the one in the book. Arrh happy days.
Sorry for being a bit off topic. But why can't they teach this sort of stuff in school. They used to.
Link for the Denshi block http://en.wikipedia.org/wiki/Gakken_EX-System

Re: Building your own computer

Posted: Fri Oct 26, 2012 3:04 pm
by PeterO
tech_monkey wrote:@ Jim.
Glad I'm not the only one.
I started out with one of these: http://searle.hostei.com/grant/Electron ... adionicX40 It even had some logic gates and a bistable to make :)
PeterO