Correspondence with David Larsen about the Overfelt Mark-8. ----------------------------------------------------------- See this Web page for context: http://www.retrotechnology.com/dri/titus.html The references in this email, are resolved in the subsequent transcript of the audio noted. - Herb Dec 30 2014, from Dave Larsen: Hi Herb - Thank you for the information and interest in the audio post. Yes, please do use this on your blog and the link [to my site] will be appreciated very much. I will send a copy with a few minor corrections. My name is with an e -- Larsen - common error for many as it is spelled with o for some - I am Danish (E) and Swedes are (O) - most of the time. My grand parents came from Copenhagen, Denmark in the 1880's. This is even hard for me to believe - my grandmother Larsen was born in 1852 passed on in 1942 or so when I was 4 years old. I am only 76 at time and going strong with several businesses in addition to the Museum. Back to the blog post - I have had your blog site link listed on mine for a long time. I am sure glad to have the interest in the Mark 8 and other very early microcomputers. I have 5 MARK-8's and all are so different - one is very crude and one was made into a very complex control computer. I don't know just what it was used for but the fellow that built it must have 100's of hours making it work for him. Here is the link to see the various efforts folks did to make their MARK 8. I have one on display in my museum, one at MARCH, and the others are just waiting in my museum warehouse for someone to put them to use or in a serious display. http://bugbookmuseum.blogspot.com/2014/04/vintage-computers-mark-8-computer-most.html Here is what inspired Jon Titus to design and publish his work on the MARK 8 . http://bugbookmuseum.blogspot.com/2014/08/vintage-computer-what-inspired-titus-to.html Have a very Happy and Successful 2015!! Again - thank you for your interest and hope to see you in Floyd VA sometime. - David Larsen , Curator ----------- Text from David Larsen's Web site, followed by transcription of phone conversation David provided as audio. David reviewed the transcript and provided the edited version below, Dec 30 2014. - Herb Johnson http://bugbookmuseum.blogspot.com/2013/02/vintage-computer-mark-8-sent-to-march.html [text on the Web page] Tuesday, February 26, 2013: Vintage Computer MARK 8 sent to MARCH in Wall NJ Hi - The MARK 8 computer I sent to the 'Mid-Atlantic Retro Computing Hobbyist' ( MARCH ) in Wall, NJ arrived yesterday 2-25-13. I am glad to loan it to them from our 'Bugbook Historical Microcomputer Museum' here in Floyd Virginia. I do hope it will be a display that folks like. Some of the members of MARCH are planning on restoring the computer to working order and putting in a nice display case so the MARK 8 cards are viewable. Here is a telephone conversation with George Overfelt about the MARK 8 and other computer topics 8-15-13 - Nice that George is still active at his age - We chat now and then by phone about this MARK 8 computer he built 37 years ago in 1976 - This added 8-15-13 - David Larsen [transscript of phone conversation] (opens with introductions, personal conversations) L(David Larsen): I wanted to tell you... we loaned your computer to the MARCH group up in New Jersey. They've got it running...Group of folks up there, they do a lot of retro-computing... O(George Overfelt): [You said] they were going to fix it, or to try to get it to work, was the last you told about. L: Well they have it running, I saw a video on it the other day, and they got it working, they are plugging away.. They are going to put a plastic case around it where people can see in it. But I think its virtually running, it may have a few little bugs in it. They checked out the power supply, it was still working. They turned the computer on & it seemed to be working, I don't think they put too much of a test on it. but it doesn't sound to be to be far from functioning. actually O: Well great! that's good news. L: It is. I'm delighted to have them use it. We've been active here with our display, so I'm glad they had time to work on it, that's just great. You know, that was an important computer.....Again, if you don't mind, give me a little brief description of just buying that thing, and putting it together...You know, what you did with it, which probably wasn't too much... O: I'm afraid it was pretty little....It was the first step, it was kind of a learning step. That's what I originally did it for. I was trying to catch up with what was going on. You know, it was in Radio-Electronics magazine, an article or two... L: Three articles actually, in 1974... O: It was actually pictured on the cover of the magazine, back there in 1974, kind of a breadboard looking thing. They were bringing out the boards, one at a time. Every time a magazine came out, they'd bring out another board or two. Until we...I kept buying the boards, one at a time, and putting them together. Finally when I got enough to assemble the whole thing, well, I did. O: Then I wanted to package it in some way, so it wouldn't look like a breadboard. So I put it in that box, which seemed to be just the right size for it. L: Oh yeah, it fit really good. It was literally a breadboard, because you had slots in a little wooden rack, you put the cards in, which was pretty cool. O: They weren't plug-in, they just ran the wires thru from board to board. it was a real kludge by today's standards. But it did go together, and it did work reasonably well.. L: Did you ever hook up a serial port up? You had a Teletype connector on there. Did you ever have a terminal or anything hooked up to it at any time? O: No, I got more interested in what else was going on by that time, there were more computers coming out. It wasn't long before the PET computer was out. And that's the route I went. I bought one of the first PETs, with the 40 character line and the little 9-inch screen and Chicklet keys. But it ran BASIC and you could really do something with it. Finally I graduated up to what they called the 8032, which was a 12 inch screen with a 80 character line. O: I actually wrote a BASIC program to put the [IRS Federal Income Tax] 1040 form on your screen. And all you had to do was fill in the numbers, and it would do the calculations. This was used on an audio tape and audio cassette. You can imagine how slow it was, it took forever to run that tape! (ha ha) But it would actually do your income tax (ha ha) one of my first accomplishments with a computer. L: Going back to the Mark-8. You spent a lot of time on that, I could tell from working with the design of the power supply. How long did it take building that unit? had to be a pretty good amount of time... O: I couldn't tell you. I wasn't keeping track..... It really was... getting all the chips, doing all that soldering. Then of course, I had to come up with a power supply, That was easy for me, being a technician, I'd been building power supplies all my life. L: Was that your first computer project? O: The first one at home. Where I worked at Sandia Corporation clear back in 1958, Sandia Corp. began building many computers, along the lines, actually before, the PDP-8. I worked for a group in Albuquerque that put together one of the first saturated logic, all solid-state computers. It ran at ridiculously low speeds. I remember the first clock speed was 100 kilocycles. Then we kicked it up to 500 kilocycles, and we really thought we had arrived. We used a Teletype for the terminal. We actually got that working so well, they put it on assembly-line check of atomic bombs in Kansas City, where they were being assembled. Realize, Sandia corp. was [originally] a nuclear weapons [firm]. O: We got that thing to work, and actually used them. We quit using the Teletype and got a Flexowriter, which was an advanced machine, which was much quieter, more modern, better keyboard and everything. It was built into a desktop, they made them here in Oakland CA. We hooked that thing up to it, and it was working pretty well. I think It was 1959 or 60, that Digital Equipment came out with a PDP-8....[likely an earlier model - Herb].. L: Let me ask you one more question about the old Mark 8. Was that a pretty good experience for you? I mean it was really a rudimentary computer, but I assume that experience was a good launch pad into the other micros... O: Like I say, I graduated to the Pet, then the XT when IBM came out with the XT's. You could clone them, you know, it was so easy to put 'em together. I built a number of the XT's.. L: Well, I can tell you, we sure appreciate getting [the Mark-8], and [after] having it stored in the warehouse for a long time, and then getting it out and getting it going again, It was pretty exciting to have it out there and operating, for me. I hope it is for you. O: (ha ha) Yeah, that's great. I never thought I'd see it running again..(ha ha) .after all these years.... [discussion about links, email addresses, and Larson sending video of it running...] - Transcribed by Herb Johnson, Dec 30 2014; reviewed and edited David Larson, Dec 31 2014.