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View Full Version : IMSAI 8080 40th anniversary?



ef1j91
December 18th, 2015, 04:53 AM
According to the IMSAI "pre-history" on IMSAI.net [1], the first IMSAI 8080 kits shipped on December 16, 1975.

[1] http://www.imsai.net/history/imsai_history/imsai_pre_history.htm

Soupwizard
December 21st, 2015, 01:34 AM
I have an imsai with the original sales receipt from the imsai corp, dated 30 April 1976. It'll be 40 years old in April! I wonder if I could get it running by then.

ef1j91
December 21st, 2015, 04:59 PM
Very cool! Was it a kit? I'm interested in hearing more about what it was like building / owning / operating the IMSAI in 1976.

jgalinat
December 22nd, 2015, 04:42 AM
Very cool! Was it a kit? I'm interested in hearing more about what it was like building / owning / operating the IMSAI in 1976.

While it's a little later than 1976, my first computer was an IMSAI 8080 that I built from a kit in 1977. While I had decent soldering skills because of a 2 year electronics degree from a local junior college, I had never built a kit of this magnitude before so I was amazed that it worked on power up. I remember soldering 1600 pins for the 22 slot S-100 backplane in one evening. I had 56k in the form of qty. 7 8k static memory boards. The memory I used was a story in itself. I worked in the service depot for a computer terminal manufacturer before I bought the IMSAI kit. The company used qty 4 4044 static memory chips for the 2k screen memory in it's terminals. However, there was an industry shortage of the 4044 chips for a period, so the the company started using a daughter board with qty 16 2102 chips in order to ship terminals. These proved problematic as the daughter boards worked loose in shipping so the company scrapped them as soon as the 4044 chips became available again. I grabbed all the remaining daughter boards before they hit the trash. I unsoldered the 2102 chips using a soldering iron & bulb sucker and only destroyed 3 chips in the process. I then populated the 7 blank 8k boards with these chips and saved a ton of money. I started with a Tarbell cassette interface but soon after purchased the North Star floppy disk system. The North Star disk system cost $700 as a kit and only stored 90k on a disk but was a huge improvement over cassette storage. The only problem I ever had was occasionally the system would hang unexpectedly and I didn't understand why. I talked to a few more knowledgeable people and we scoped the bus lines and they were very noisy. The root of the problem was that I put all the boards at the front of the machine so the rear connectors had no load on them and the bus was "ringing". The quick fix was to move some of the memory boards to the rear of the machine. I soon purchased a S-100 terminator board kit and never had another problem. We used to play a lot of BASIC games on the system and I also purchased a Newtech model 6 music board to play some tunes to entertain friends. Sorry to be so long winded but I wanted to give you an idea of some of the things I did to save money. The stuff was so expensive so the money I saved on the RAM allowed me to build the floppy disk system. Let me know if you have any questions.
Jeff

peclark
December 23rd, 2015, 07:24 AM
Awesome story! As I was reading I got a mental picture of you unsoldering all those chips :) It reminds me of some of the stuff like that I did back in the day when I had no money as well. It seems it's almost always true that necessity is the mother of invention.