#u880 — Public Fediverse posts

Early Sunday was used to solder the last lines of the #KramerMC memory expansion. All lines are beeped, correct and not shorted. Now I have to wait for my memSIM2, which is in repair in the moment. The voltage regulator was melted, no one knows exactly why.
#RetroComputing #FormerGDR #KitComputer #ZilogZ80 #U880

After some searching I found the problem in #KramerMC. The #DS8286 on the cpu board gets in the way. In addition, it is installed incorrectly because the inputs and outputs are bridged. When I leave the socket empty it runs fine. Wonder if the computer ever worked the way it was intended.
Since I still had two of the plug-in contacts for the bus system in stock, I'm starting to build a RAM expansion to 64k. With address decoding to spare out 0000-0fff (ROM 2732) and 0fc00-ffff (display RAM). Because of the simplicity I decided to use 64k static RAM.
I'm also curious if the buddy might bring a new CPU board today, I'll be surprised.
#RetroComputing #Z80 #U880 #FormerGDR

You like some #KramerMC news? After the last try it doesn't work properly again. Which doesn't surprise me with the catastrophic condition of the CPU board. I'm tired of looking for broken wires/cuts again and again. We decided that a colleague in the museum would etch the whole thing again from scratch. And I would then build a "new old" one, of course with the original parts.
At the moment I'm revising the layout scanned in 1200 dpi in GIMP. It's always a bit of a loss when it's 35 years old and printed on extreme eco-friendly paper.
#RetroComputing #Zilog #U880

Today's afternoon in the museum wasn't really successful at all. I carried my EPROM simulator (memSIM2) with me to make a few tests with the real #KramerMC. But the beast wasn't thankful using it after a sleep of two years. Nothing broke, but it doesn't do what it supposed to do. A small test program filling the CRT memory with various characters. But I used the time and revised my git repo so that now all required programs under DOS and Linux with their instructions are part of it.

But I won't give up that easily. But the others asked me what I would do if one day the computer ran without errors 😂​
#RetroComputing #Zilog #Z80 #U880

Now I'm curious who knows the #KramerMC, or more uncommon who has ever seen one in real life.
At the end of the 1980s, a book by #ManfredKramer was published by the military publishing house of the GDR. It described how to build your own computer based on the 'Zilog' #U880 CPU. The book goes into many details, including monitor listings, circuit board layouts and technical details.
The example on the pic comes from the person who developed the circuit board layouts at the time. It has a personal dedication from Manfred Kramer and so it appears to be No. 2 of the KramerMC. In parts it is still usable, at least its display preparation is working again after extensive repairs.
#RetroComputing #GDR #Zilog #Z80 #ComputerMuseum