SX 64 I/O board

Commodore SX 64 I/O Board

  • only two versions known (to me) 251106 Rev A and 251106 Rev 1, difference seems to be capacitor c9 that is missing in Rev 1.
  • contains the logic and two CIA’s that the SX uses to communicate to external equipment like drives, printers and modems (and internal drive)

Integrated Circuits

PCB Identifier Chip NumberRemarks Memory Location/bit
UC1 4066
UB26526
CIA 1$DC00-$DCFF
UB36526
CIA 2$DD00-$DDFF
UD27406
UE274LS74A
UE3556

Schematics

Commodore SX 64 I/O Board Schematics 251107

Commodore SX 64 I/O Board Schematics 251107

Board Image

251106 REV A

251106 REV A

251106 REV 1

251106 REV 1

5 Responses to SX 64 I/O board

  1. Ken says:

    interesting about the C9 on the rev 1
    I just ran into that issue installing a switchless jiffydos board
    I think c= directly soldered it to the 556 on that version
    if you look at the 2 picks of UE3 v1 has a resistor soldered on as a afterthought and the other its on the board properly marked as C9

  2. Ken says:

    um my bad UE3 has a capacitor …not resistor
    shouldn’t try and type before my morning coffee

  3. Michael J Betz says:

    Schematic lists:
    UC1 should be 4066
    UE2 should be 74LS74
    UB2 should be 6526A CIA
    UB3 should be 6526A CIA
    UD2 should be 7406
    UE2 should be 74LS74
    UE3 should be 556

  4. Michael J Betz says:

    Actually the circuit list is all wrong….

    • Jeroen says:

      Dear Michael,

      Thank you for telling me,
      I listed the parts list of the floppy disk controller card instead of the I/O card.

      I fixed the error.

      Regards,

      Jeroen.

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