Hello! I have been quiet for some time, but I spent that time productively ;-) In this blog post, I have coined a probable theory explaining why the 8088 board does not work in Commdore 610: http://www.cbm-ii.com/commodore-610-and-720-chip-inventory-comparison/ Basically, according to the schematics, the chip U20 is supposed to be 74S86 quad XOR gate (with Schottky diodes). But on my 610 board, it is a plain 7864, which is a slower version. Coincidentally, this very chip is used to feed the memory RAS signal to the 8088 board! Having a slower chip provide the signal to the board may very well cause memory control signals to arrive too late under certain conditions, which is a perfect explanation for memory corruption problem experienced under the 8088 board. There is also U13 which is supposed to be 7486, but is 74LS86 on my board, which can be a culprit here, though my bet is on U20. You may check your 610's too to see what chips you have in these places. I will order a 74S86 and try to make a replacement. Regards, Michal Pleban Message was sent through the cbm-hackers mailing listReceived on 2011-04-04 20:00:13
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