Author Topic: homebuilt computer, and more  (Read 5568 times)

Offline vtsteam

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homebuilt computer, and more
« on: April 05, 2015, 08:28:44 PM »
I just love this site:

http://www.homebrewcpu.com
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline sparky961

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Re: homebuilt computer, and more
« Reply #1 on: April 05, 2015, 10:10:55 PM »
Thanks for sharing this. I wish I had been born a few decades earlier when computers were this simple.

Offline Pete.

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Re: homebuilt computer, and more
« Reply #2 on: April 06, 2015, 02:38:01 AM »
Well I'm glad I didn't have to grow up with computers that complicated :)

Offline AussieJimG

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Re: homebuilt computer, and more
« Reply #3 on: April 06, 2015, 03:50:56 AM »
I built the EDUC-8 in Australia in the 1970s. It was designed by one of the journos working for Electronics Australia after he did a course on the DEC PDP8 and was published in that magazine. It used the 74141 CPU (IIRC) and used gates as gates, counters as counters, encoders as encoders and so on. I finally found out why they were called that.

Here is a link: http://www.ljw.me.uk/educ8/

Jim

Offline vtsteam

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Re: homebuilt computer, and more
« Reply #4 on: April 06, 2015, 10:49:09 AM »
I built an LNW-80 from bare unpopulated PC boards, but that used a Z-80, not microprocessing from chips. I did do some wire wrapping for a homemade EPROM programmer, and an interface for a converted IBM Selectric terminal for a printer. But that was minor compared to what the guy above did!

I really like his other projects page too! He's just cool digital retro in my book!
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline awemawson

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Re: homebuilt computer, and more
« Reply #5 on: April 06, 2015, 12:10:16 PM »
I designed and made a 'bit slice' computer back in 1973/4 using the 74181 four bit logic slice family. All wired using very thin  'burn through' polyurethane insulated copper wire on epoxy copper prototype boards etched on the kitchen table  :ddb:

Took hours and hours - but it worked !  The main cpu bit slice performed simple boolean operations such as shift, add, or, nor etc and these were built up into more complex functions using microcode hard programmed with a diode matrix that could be called a rom I suppose.
Andrew Mawson
East Sussex

Offline S. Heslop

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Re: homebuilt computer, and more
« Reply #6 on: April 06, 2015, 01:33:08 PM »
Thanks for sharing this. I wish I had been born a few decades earlier when computers were this simple.

When I was a kid I got real excited about computers, this must've been around the start of the 2000s. I went to the library to get some books out on the topic but by that time all the books they had were of the 'windows 95 for dummies' variety. It was frustrating since I couldn't find any computer information worth a damn and kept reading that rubbish hoping to learn something. I think if I was born in the 70s I would've had a whale of a time with the computers that came out in the 80s.

Offline Lew_Merrick_PE

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Re: homebuilt computer, and more
« Reply #7 on: April 06, 2015, 03:55:43 PM »
Ah, my first micro-computer was a 4-bit, discrete component, RTL processor running at a (then) screaming 16 kHz.  It had 256 BYTES of magnetic core memory and was programmed with bat switches with "output" on grain-o-wheat bulbs.  It ran it's first program in the spring of 1968.  I added a paper-tape reader to it in the winter of 1968.  [My brother's high school sweetheart was a member of the ARPA team at MIT and needed somebody who could "cut" PC boards and solder.]

Offline Swarfing

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Re: homebuilt computer, and more
« Reply #8 on: April 06, 2015, 03:56:15 PM »
Just thought I would share some my history which started with my mother who worked at Plessey Semiconductor in my home town.

http://www.swindonweb.com/?m=8&s=116&ss=396&c=1327

Her claim to fame was working on the prototype silicon wafers for the first SIL's DILL's and quad flatpacks that put a start to some of the endeavours seen in this thread. My real start was a plain brown cardboard box with the contents of a beige Sinclair ZX80 that you had to put together yourself. I so longed for the day when i could afford a new fandangled mouse for my NEC 8086 4mhz proc and no maths co-processor. Thought i was the bees knees learning assembler and fortran as a kid. We all knew more than the teachers who tried to teach us computer programing as well.

Remember saving up for 128k or 256k DRAMS to populate your memory boards? Cutting holes in your 5 1/4 floppies to get more data on the other side? Real computing days.

Once in hole stop digging.

Offline vtsteam

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Re: homebuilt computer, and more
« Reply #9 on: April 06, 2015, 04:10:23 PM »
I'm sort of in between you and the earlier guys here, swarfing -- I do remember the ELF coming out in the pop electronics mag, but couldn't figure out what i was good for.  But a couple years later did know! And was saving up for 4116s to piggyback dead bug style on top of the 4K memories I had in a 6802 powered Color Computer. I think 16k was about $100 then.

I remember admiring the Sinclairs, actually, especially the price, but being on the wrong side of the Atlantic.

The LNW-80 had about 100 IC's to find (surplus mostly) and populate. And I don't know how many support components....hardest part to locate for me actually turned out to be the clock crystal!

I programmed the EPROMS myself, and overclocked the Z-80 to 5.33 mhz compared to the under 2 mhz of the TRS-80 model 1 which it was similar to. This was a "high resolution" color computer, too -- before the IBM PC came out, and higher resolution and faster even after it did. I did eventually get an original IBM PC (still have it) but it was a definite step back.

I programmed the LNW in FORTH, and wrote a wire frame graphics program to rotate and display boat lines in color and 3D from a table of offsets. At that time a terminal to do the same cost $20,000.

By 1991 it was outdated enough that I set it on top of the dustbin in front of my house, and hope somebody would take it before it was trashed.
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline beeshed

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Re: homebuilt computer, and more
« Reply #10 on: July 12, 2015, 07:13:54 PM »
Only just noticed this thread.
Any one else a member of the Amateur Computer Club back in the seventies?
The ACC published a design based on a state machine ALU in about 1975 and the '7768' using the 6800 in 1977 which I built at work on a bit of double sided pcb I found. Those days we were still hand drawing boards and etching in a tray on our desk for prototypes for satellites and military electronics. I scrounged a few of the chips but had to buy the Micro for 30 as we weren't using anything so advanced at work. 256 bytes of ram, 8 data and 8 address switches and 8 LEDs for output. Later added video and 32k ram.
Anyone go to the London Computer Fairs in the '80s run by the Associatonof London Computer Clubs?
I was amused by the comment in the starting link about 128k being enough memory to do something useful. My first wordprocessor was just 2k and even had line justification.

Offline Auskart

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Re: homebuilt computer, and more
« Reply #11 on: July 13, 2015, 04:58:19 PM »
I built this one back in 1978, fun but not really functional.

http://www.chookfest.net/computers/miniscamp.html

Offline rythmnbls

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Re: homebuilt computer, and more
« Reply #12 on: July 13, 2015, 05:32:39 PM »
I built this one back in 1978, fun but not really functional.

http://www.chookfest.net/computers/miniscamp.html

Wow what a trip down memory lane.

I built the Dick Smith kit version of the Miniscamp in '79, it had 256 bytes of ram and no e/p/rom at all. Ram was programmed by halting the cpu with a switch, tristating the buses with the dma switch and loading byte data into each ram location by setting address and data values with front panel switches and pressing the load/deposit button, a write speed of about 2 bytes / minute :)  I never did anything useful with mine except for the usual counting programs.

It was a great learning tool and today I still make my living in the world of computers.

Best Regards,

Steve.

Offline Auskart

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Re: homebuilt computer, and more
« Reply #13 on: July 13, 2015, 10:15:05 PM »
Yes I remember programming the Miniscamp by the front switches, get 3/4's of the way through and then forgetting where you were up to in the program, great fun having to start again.  :doh: