Editing SixtyClone Bare-Board Project

{{Infobox hardware
| name           = SixtyClone “Bare-Board” Project
| image          = [[File:SixtyClone_250407_PCB.jpg|260px]]
| caption        = Green-solder-mask SixtyClone 250407 replica PCB (rev b)
| developer      = “Bob’s Bits” community project (lead: Rob Taylor)<br />contributors incl. Jim Drew, Leif Bloomquist & C64 enthusiasts world-wide
| type           = Drop-in replica Commodore 64 mainboard (bare PCB only)
| first_released = late 2016 (initial 250407 gerbers uploaded)
| latest_release = rev E gerber set (2022) – 250407, 250466 & 250469 variants
| layers         = 4-layer FR-4, ENIG finish, gold fingers
| compatibility  = 100 % electrical* with original C64 ICs & shields<br />(*one bodge wire on early rev A to route VIC /Φ0)
| features       = • modern 4-layer impedance control<br />• enlarged silkscreen legends & test-pads<br />• optional dual-kernal footprints + JiffyDOS jumper<br />• consolidated decoupling network & “silk-BOM” printing
| model          = SixtyClone-250407 / -250466 / -250469
}}

The '''SixtyClone bare-board project''' is an open-hardware effort to recreate every major revision of the Commodore 64 logic board as brand-new, professionally-fabricated PCBs.  
Designed so that hobbyists can '''transplant the original MOS/CSG chips''' from a corroded or broken donor machine into a fresh board, SixtyClone provides a legal, royalty-free alternative to scavenging vintage hardware. The gerbers (and KiCad sources for recent revisions) are released under a permissive licence; commercial runs are sold via Bob’s Bits on Tindie and by several regional group-buys. 

== Project goals ==
* '''One-to-one electrical compatibility''' – keep every trace, pad and via placement true to Commodore’s own artwork so that RF shields, heatsinks and cartridges still fit.
* '''Manufacturability upgrades''' – convert the 1980s 2-layer stack-up into a modern 4-layer with internal ground/power planes which greatly reduce crosstalk and audible VIC “jail-bars”.  
* '''Usability improvements''' – large white silkscreen labels (including capacitor values) double as a printed Bill-of-Materials; mounting hole diameters match today’s metric M3 hardware.  
* '''Educational licence''' – gerbers are free for personal use, encouraging new builders to learn through-hole soldering while preserving classic computers.   

== Supported C64 revisions ==
{| class="wikitable"
! SixtyClone variant !! Original Commodore PCB !! Key differences / notes
|-
| SC-250407 || “long-board” breadbin (1983-85) || Most common donor; retains separate 6581 SID & 12 V rail
|-
| SC-250466 || late breadbin (1986) || Two 4464 DRAMs, 8562/8565 VIC, color RAM integrated in PLA
|-
| SC-250469 || short-board / 64C (1987-92) || HMOS chips, 9 V SID supply; optional pads for dual-kernal switch
|}

Early SixtyClone rev A boards required a bodge wire between VIC pin 38 and the CPU ϕ0 trace; this was fixed in rev B and later. 

== Bill-of-materials overview ==
Because SixtyClone is '''just the PCB''', builders must source every through-hole component:

* 21× logic ICs (74LSxx), 16× passives, crystal & can oscillator  
* PLA, CPU 6510/8500, VIC-II, SID, two CIAs – taken from a donor or aftermarket replacements  
* three linear regulators & heat-sinks (250407 only)  
* 4700 µF + 1000 µF axial electrolytics (footprints accept radial if leads are bent)  
* DIN keyboard, cassette & power connectors – modern CUI / Cliff equivalents fit the footprint  
A colour-coded silk-screen value is printed beside every capacitor and resistor to speed hand assembly. Detailed spreadsheets, Digikey/Mouser links and pick-lists are maintained in the project GitHub wiki.

== Assembly tips ==
# '''Wash & dry the PCB''' to remove fabrication flux; ENIG finish is already tinned.  
# '''Install low-profile parts first''' (res-networks, jumpers, resistors) followed by sockets and electrolytics.  
# '''Tin the stitched-via grounds''' under each TO-220 regulator (250407) before mounting the heatsink to guarantee low-impedance bonding.  
# '''Perform continuity checks''' on the 5 V and ground planes *before* inserting irreplaceable MOS chips.  
# Recommended to pair the build with a modern “C64 Saver” PSU protector when first power-up.

== Known issues ==
* '''SID audio hum''' – greatly reduced versus original boards but still audible on high-gain amplifiers; adding a ground-lift plane under the audio path (rev E experimental) lowers the noise a further 3 dB.  
* '''Keyboard bracket height''' – certain aftermarket metal keyboard braces foul the cassette port shield; trimming 1 mm from the bracket front edge resolves the clash.  
* '''Case LEDs''' – early silkscreen marked +/- backwards; always verify polarity before soldering.   

== Licensing ==
Gerber and schematic files are released under '''Creative Commons BY-SA 4.0'''. Commercial resale of finished boards is permitted provided attribution remains on the silk-screen and in accompanying documentation.

== Availability ==
* '''Tindie storefront “Bob’s Bits – Commodore 64 replica PCBs”''' – sells 250407 & 250469 boards in green, blue and black solder-mask, typically US $29 – $35 each.   
* '''Group-buys''' on r/c64 and Amibay several times per year, often bundled with complete BOM kits.

== External links ==
* [https://retrohax.net/sixtyclone-commodore-64-replica-pcb-build-log/ Retrohax build-log & high-resolution photos]  
* [https://github.com/bobsbits/SixtyClone Official GitHub repository – gerbers, KiCad source & BOM]  
* [https://www.tindie.com/products/bobsbits/commodore-64-replica-pcbs/ Tindie product page]  

== Related pages ==
* [[C64 Reloaded MK2]] – a professionally-re-engineered C64 logic board with CPLD PLA  
* [[Ultimate 64 Motherboard]] – FPGA-based SoC replacement  
* [[Commodore 64 Capacitor Replacement Guide]] – recommended before transferring ICs to SixtyClone  
* [[PLA Replacement Options]] – modern substitutes for the 906114-01 in long-board builds  

[[Category:Commodore 64 Modifications and Enhancements]]
[[Category:Commodore Systems]]