[cctalk] Re: recreating old computers [was: Paper tape in casettes...]

On 2/27/24 20:34, CAREY SCHUG via cctalk wrote: A 360/30 could be a real problem.  It used air bags to push the microcode cards against the bit line boards.  Those air bags looked suspiciously like IV bags from the hospital.  I can't imagine they would still hold air after 50 years. The 360/40 had mylar cards with flex-print to make the microcode word lines, these were punched to break the lines so they went either through, or around the sense transformers to select a 1 or 0 for that bit.  Old mylar tends to crack, and I assume that would break the conductive printing. The 360/50 and /65 had capacitive microcode read only storage which consisted of bit line boards with copper squares and word line boards that had zig-zag word line traces that had either the drive line or balance line widened to cover the bit line square, to select 1 or 0.  These boards were separated by a 1 mil mylar sheet, and squeezed by a spring-loaded metal plate and a foam pressure spreader.  I think these have at least a SLIGHT chance of still working after 5 decades. The power was not real high on these machines, although the peripherals could draw a lot.  The 360/50 and /65 CPUs drew just a couple KW each. Of course, the models /50 and /65 were a LOT bigger than a /30, and much heavier.  There's a reason people used to talk about "big iron". As for the logic, the 360's used SLT, a 1/2" square ceramic hybrid with, generally two transistors, 4 diodes and 4 resistors per package.  The complete schematics for all of them are in the FEMM, and I'll bet one could replace them with a tiny PCB with SOT23 transistors, etc. to replace any bad modules. Jon