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 Number | Remarks | Memory Location/bit |
|---|---|---|---|
| UA1 | TMM2016P | RAM | $0000-$07FF |
| UA3 | ROM | $E000-$FFFF | |
| UA4 | ROM | $C000-$DFFF | |
| UB2 | 74LS04 | ||
| UBC3 | 6522 | VIA 1 (I/O) | $1800-$180F |
| UBC4 | 6502A | CPU | |
| UC2 | 74LS00 | ||
| UD2 | 74LS42 | ||
| UD3 | 74LS86 | ||
| UD4 | |||
| UDC5 | 6522 | VIA 2 (Disk) | $1C00-$1C0F |
| UE2 | 74LS14 | ||
| UE3 | 7406 | ||
| UF2 | M54532P ULN2064 | ||
| UF3 | 7404 | ||
| UF5 | GATE ARRAY | ||
| UG4 | 7407 | ||
| UG5 | 74LS193 | ||
| UH1 | 592 | Video AMP | |
| UH4 | 9602 | One Shot | |
| UH5 | 74LS197 | ||
| UJ1 | 592 | Video AMP | |
| UJ4 | 74LS86 | ||
| UK4 | LM311 | Comparator |
Schematics
Commodore SX 64 I/O Board Schematics 251107
Board Image
251106 REV A
251106 REV 1
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
um my bad UE3 has a capacitor …not resistor
shouldn’t try and type before my morning coffee