Editing Commodore VIC-20 Troubleshooting Guide (section)

== Model overview ==
The entire VIC-20 range shares a '''6502 CPU clocked at ≈ 1 MHz, 5 KB of on-board SRAM, twin 6522 VIAs and a single VIC chip that generates 22 × 23 text, colour, sound and the φ2 CPU clock.'''  
* '''NTSC''' boards: MOS 6560, 14.318 MHz crystal, 60 Hz video.  
* '''PAL''' boards: MOS 6561, 17.734 MHz crystal, 50 Hz video.  

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''Major motherboard revisions'''
! Assembly !! Power connector !! Regulator inside computer !! RAM layout !! Notable changes
|-
| 324003 (early) || 2-pin AC || 7805 + fuse || 11 × 2114 (1 K × 4) || Large PCB, nearly every major IC socketed
|-
| 250403 “CR” || 7-pin DIN || External 5 V, internal 12 V doubler || 2–4 larger SRAMs (e.g. 6116) || Smaller PCB, fewer sockets, cassette motor driven by Q3 + Q4 + CR1 zener
|}