Interactive Connector Diagram
Click or tap any pin in the diagram below to inspect its signal assignment, electrical specification, and wire colour standard.
Click any pin to view its signal assignment, electrical spec, and wire colour.
Supported Systems / Found On — Retro Machine Hubs
This connector is used on the following retro computer systems. Click any colour-coded badge below to open its full board-level repair, diagnostic, and schematic Machine Hub:
Connector Specifications
C64 / C128 / SX-64
2×22 Contacts, 0.100" (2.54mm) pitch — /EXROM (Pin 9) & /GAME (Pin 8) control banking
VIC-20 Slot
2×22 Contacts, 0.156" (3.96mm) pitch — /RAM1–3 ($0400–$0FFF) & /BLK1–5 ($2000–$BFFF)
C64 I/O Pages
Pin 7 = /IO1 ($DE00–$DEFF) | Pin 10 = /IO2 ($DF00–$DFFF, REU / Action Replay)
Dead Test Mode
Grounding Pin 8 (/GAME) with Pin 9 (/EXROM) High forces Ultimax Mode ($E000–$FFFF bypasses PLA/Kernal!)
Full Pin Assignment & Wiring Reference
| Pin | Signal Name | Direction | Electrical Spec / Role | Wire Colour / SCART / Adapter Target |
|---|---|---|---|---|
| Top 1, 22 / Bot A, Z | GND (0 V) | GND | 0 V Ground on all four outer corner pins (1, 22, A, Z) | Black (GND) |
| Top 2 & 3 | +5.0V DC | Pwr | +5.0 V DC Cartridge Supply (~450 mA max for REU / 1541 Ultimate / Kung Fu Flash) | Red (+5V) |
| Top 4 & 5 | /IRQ (4) & R/W (5) | I/O | Pin 4 = /IRQ Interrupt | Pin 5 = CPU Read/Write | Control |
| Top 6 | DOT CLOCK (8 MHz) | Out | 8.18 MHz (NTSC) / 7.88 MHz (PAL) Dot Clock | Clock |
| Top 7 | /IO1 ($DE00–$DEFF) | Out | Active-Low I/O Block 1 Chip Select ($DE00–$DEFF) | Purple |
| Top 8 | /GAME | In | Active-Low Cartridge /GAME sense (Low alone = Ultimax Dead Test mode!) | Blue |
| Top 9 | /EXROM | In | Active-Low Cartridge /EXROM sense (Low = 8KB Cart at $8000; Both Low = 16KB) | Green |
| Top 10 | /IO2 ($DF00–$DFFF) | Out | Active-Low I/O Block 2 Chip Select ($DF00–$DFFF) | Purple |
| Top 11 | /ROML ($8000–$9FFF) | Out | Active-Low Low Cartridge ROM Chip Select ($8000–$9FFF) | Orange |
| Top 12 | BA (Bus Available) | Out | VIC-II Bus Available output | Yellow |
| Top 13 | /DMA | In | Active-Low DMA Request input (halts 6510/8502 for REU / SuperCPU) | White |
| Top 14–21 | D7 – D0 (Data Bus) | I/O | Pin 14 = D7 (MSB) down to Pin 21 = D0 (LSB) | Green (Data Bus) |
| Bot B & C | /ROMH (B) & /RESET (C) | I/O | Pin B = /ROMH ($A000–$BFFF or $E000–$FFFF Ultimax) | Pin C = /RESET | Orange |
| Bot D, E, F | /NMI (D), PHI2 (E), A15 (F) | I/O | Pin D = /NMI (Freeze button!) | Pin E = PHI2 1 MHz Clock | Pin F = A15 | Clock/Ctrl |
| Bot H – Y | A14 – A0 (Address) | Out | Pin H = A14 down to Pin Y = A0 (LSB) | Blue (Address Bus) |
How a Dead Test Cartridge Boots a Black-Screen C64 (Ultimax Mode)
Both the C64/C128/SX-64 (0.100" pitch) and the VIC-20 (wider 0.156" pitch) use a 44-contact (Top 1–22, Bottom A–Z omitting G, I, O, Q) rear cartridge expansion connector that gives external cartridges complete control over the 6510/6502 memory map.
- By pulling Pin 8 (/GAME) to Ground (0 V) while leaving Pin 9 (/EXROM) High (+5 V), a Dead Test cartridge forces the C64 PLA into 1982 MAX Machine ("Ultimax") mode: the cartridge's /ROMH chip select (Pin B) maps directly to $E000–$FFFF (the 6510 Reset Vector!), completely bypassing a dead onboard Kernal ROM, BASIC ROM, or low RAM!