Saturday, January 9, 2016

Continuing to debut 2310 function, plus news from Finland


Johannes had a failed SLT board that had to be repaired. He was successful in transplanting the needed modules from spare boards to bring the repaired board back to life. The level of integration and technology in the 1130, 360 and 1800 is just at the edge of where they can be repaired even if no exact spare parts exist. Later generations of mainframes have embodied many of the logic circuits inside IBM assemblies such as the Thermal Conduction Module (TCM) or proprietary IBM integrated circuits for which no independent source exists.

Repair of the 360 era machines can be through transplant of IBM components, as Johannes has proved. This could even include creation of substitute circuitry consisting of germanium transistors, diodes and resistors to replace an SLT module (ceramic can that sits on the boards). Some of the parts on the SLT boards are discrete transistors and resistors or capacitors either singly or in multi-part components, all of which have replacements that can be sourced from other manufacturers.


The python program was modified to pause after it has completed a disk read or write, allowing me to put the 1130 in single step mode, check data areas and then step through the interrupt handler once I allow the PC side to continue. This will be a big help while debugging the new interaction between PC and fpga sides.

Testing pointed me at some issues in the FPGA logic which I will work on a bit. They involve the handling of the operation complete bit, which does not seem to be returned properly when the 1130 issues the XIO Sense Device. Also, the program is not getting far enough into its code to have issued the seek to a new cylinder.

I made some headway and updated some logic that I think was causing my problems. It was good to know that I was triggering the interrupt and then resetting it when the Sense DSW executed, which shows the mechanism is generally sound.

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