Getting 32K Again
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by Bill Degnan - 12/09/2022 10:38 |
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Armed with the likely EMA jumper values for an 8K core stack, I set to test every board related to memory so I could weed out the bad board(s). Fortunately I have some spare boards, enough to make 40K. 4 sets are needed for a full 32K. Two bad boards found. For future reference, the good boards are installed in the PDP 8e and the two bad are listed here, for future repairs: G111 -electrical fault or some kind. When installed the board does not communicate with the CPU. HYPOTHESIS - The board seems to be jumpered for the 8-16K space but maybe the jumpers' solder or a related component have a short and thus not able to report as being for the 2nd 8K memory space? A future project. One of the core boards (H212) is dropping bits. If I toggle in from 0000 0000/7001 6046 6041 5002 5000 when I examine address it's ok until you get to 0008, examine 0008 and we don't see 5000. Instead it's: 000 000 000 000 (0000) rather than +0+ 000 000 000 (5000) (where + = light 0 equals light off) So future me, if you're reading this now, I'd guess the G111 is fixable, more so than the actual H212 core board. Reply |
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