Recent content by Richard L

The word opposite JAPAN on my lights is RODAN. As you might image, an online search of RODAN and JAPAN yields tons of completely different images :). But there is an image of a similar light on the Surplus Sales of Nebraska website for a RODAN neon bulb. A bit different than mine, but I wonder...

I have also started incorporating some micro lights on the front panel that I found during one of my many searches for vintage parts. These seem to match pretty closely the parts seen in online photos of the original Kenbak, as well as the description given in the manual. I found only white...

I now have 3 extra 1404A shift registers tied in to my Kenbak-1 replica, acting as memory pages 2, 3 and 4 for the octal range 200-377. I had to create and add two more level shifters using the same circuit as shown in the original schematics, because the extra shift registers were too much for...

So, the extra program steps to preserve and restore 200 through 203 aren’t necessary. Carry and overflow are handled in the hardware without those steps. Also, I think monitoring the LC signal would be better than monitoring the whole L register for location 177 so I’ll try that in the future.

Attached is a link to a short video showing my replica running with paging working. I modified the "Example of Console Use" program in the Programming Reference Manual to add a bunch of extra steps to preserve and restore locations 200 through 203 while switching between pages 1 and 2. Seems...

I updated my Kenbak prototyping setup so I could pull out more signals to try different things. In addition to the two wire wrap boards connected through the slot in the Kenbak's front panel that bring out the lights and switches (and some signals) to my "terminal" seen in the lower right of...

I finally got around to implementing memory expansion as Thomas describes. It works basically just as he wrote above, except for some reason I have to write to locations 175 and 176 to get it to work, instead of location 177 which I tried to do. There must be some detail about the L register...

That does sound like a good approach, I'll give it a try. My attempt was to see if I could expand into some C1101 RAM I had taken from another board, and I was trying to alter the original logic from the diagrams in the manual to do it, using my "simulator" in Digital. I did also try to use a...

I have been spending time on and off trying to get more memory into my replica, but have not been able to figure out how to integrate an expansion into the existing serial architecture. I used a program called "Digital" to simulate the Kenbak down to the gate level so I could try various...

I need direct access to the Write Time (WT) and Overflow (OV) signals, plus I needed to make a slight logic modification to the WT signal used by the 1404 shift registers, so I made up a daughterboard that plugs into the appropriate locations. My replica is already all socketed so no mods to...

I finished the basic structure of the interface card (and added another underneath since there was room). Also finished the cable - it's based on something I found in a lot of old hardware from a Texas Instruments auction years ago. I need to have both data and control lines for the Remex...

I didn't want to drill any more holes or slots in the case so I dug up some nice vintage Cinch connectors that fit the existing front slot holes pretty well, and put them together so I could plug in an interface card inside and a cable to the peripheral on the outside. The Remex documentation...

I'm a little surprised there hasn't been discussion of the Kenbak-1 50th anniversary so far, maybe there will be as we get closer to September (the date of the Scientific American issue in 1971 with the advertisement). I had been wanting to build a replica using the period-correct parts I've...