Labels:text | screenshot | font | black and white OCR: KAYPRO II/IV 256K RAM UPGRADE - THE ANSWER TO THE PROBLEM ====== ===== Ron Rock had problems with my 83 Kaypro II/IV 256K upgrade. I hope the following will help him and others. I also hope that those of forgive me. you who didn't spot my two typing mistakes will be generous and Ron found that after installing the mod while still using 64K chips that small programs worked but large ones didn't. This suggested to me that different parts of RAM were being addressed simultaneously. I had this at one stage whilst debugging my prototype although from a different cause. NOW FOR THE CAUSE AND CURE :- My circuit as published has PIO 1 and A14b coming from U3 labelled the wrong way around. I accept full responsibility for this mistake it slipped past all my checks. Pins 10 and 11 of U3 (the 74LS153 ...
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