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    Difference between the two basic rom 11&19?

    I have 6540-019 in my PET 2001-8C, apparently there might be a -011 instead. As far as I can determine they differ in 15 bytes, in this area: -011 version: .C:c584 A2 68 LDX #$68 .C:c586 86 65 STX $65 .C:c588 68 PLA .C:c589 8D FD 01 STA $01FD .C:c58c 68...
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    PET 2001-8C glitches when screen is redrawn/cleared...

    ... and also upon pressing enter when entering a line of program in BASIC. Looks like this when running Fire! https://www.youtube.com/watch?v=Ey8gmapT_3I It's small horizontal lines in a diagonal kind of pattern, appears on every screen update in the clip as far as I can see, quite...
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    Test 6550 RAM?

    I successfully tested all 6540 ROM with the Willem eprom programmer, a breadboard, 74LS14, machined socket and a lot of breadboard wires... Turns out one was bad, got glitches here and there when reading, it never verified correctly. So, thinking if there's a neat way to test the 6550 RAM...
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