Wednesday, October 29, 2014

Successfully booted DMS2 from the internal disk drive and began building the SAC interface hardware.

Very busy with tasks from my day job, but I was able to grab a couple of hours with the system and made good progress in that time. starting manufacturing the logic/voltage conversion hardware that will interface the Storage Access Channel cable from the 1130 to TTL logic.


I checked over the cold start card data I had written down, spotted a couple of transcription errors and fixed them. After toggling the eighty words into core and readying a disk cartridge with the DMS2 monitor installed, I booted up the 1130! I head it seeking and reading multiple sectors and then drop into its I/O wait condition. The IAR read x002A and the accumulator (ACC) has x6000 which means the 1132 printer is not ready - exactly what would happen since I didn't have the printer powered up.

This is a very strong test of the system, both the 1131 processor and the disk drive, much stronger than the diagnostics I have been able to toggle into the machine so far. Once I have either the 1053 or the 1132 ready to print, I can run even more - DMS2 can be set to print on the console printer as an alternative to the line printer, plus the input commands can be rerouted from the 1442 card reader to the keyboard. I would need to have the 1132 appear ready, even if the hammers are not causing readable impressions, just to allow DMS2 to be ready to read. Then, I would have to nurse one card through the 1442, // TYP, which redirects input to the keyboard.

That would allow me to type in some job control (monitor) and supervisor cards. I could run programs, at least those that will allow all its critical input to come from the keyboard or keyswitches and don't need to print or read cards.


Until the disk heads can be thoroughly cleaned and inspected, I will not be putting any cartridges into the Diablo drive. I may experiment a bit to get sense DSW to respond for the disk drive and line printer device address that the interface implements.

I am not sure what addresses it uses, although the printer is called a 1405 which implies it may use the same area code as the IBM 1403 printer. Similarly, I expect the diablo disk to appear as one of the standard addresses that are used by DMS and the disk oriented utilities.


I am not happy with the security of the connections put onto the SMS socket pins, suspecting these are leaning over, shorting together wiring to cause the balky behavior of the keypunch. I found some push on connectors that fit much better than the current ones I installed. Once I rewire this with the improved connectors and am satisfied, I will go back to the testing.


All my supplies came to day and I started construction. I slightly modified my plan for the board layout in order to make assembly easier. Now, each board will implement twelve drivers across the top half and twelve receivers across the lower half. I have built 25% of one board so far, before the light faded outside where my assembly table was set up.

Top shows three driver circuits, bottom has three receiver circuits

The circuits are packed tightly together, each requiring five vertical columns with the input at the leftmost column and the output at the rightmost one. The horizontal power strips are +5V and ground, but the receiver circuit also needs +3V which is an SLT requirement. The +3V will connect to the number two column of each five - you can see the open hole at the top  and near the bottom of the second column, where I will daisy chain the +3V down to a connection point at the far right of the board.

I have the parts to assemble circuits for all 77 signals that are carried on the Storage Access Channel interface. This will require four boards, whose total capacity would be 96 signals if they were needed, with twisted pair in the SAC cable hooked to these circuits. The TTL side of these circuits will be wired to a high density connector which I can use to connect other logic into this voltage conversion interface. 

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