Editing C64 Reloaded MK2

{{Infobox hardware
| name              = Commodore 64 Reloaded MK2
| image             = [[File:C64-Reloaded-MK2-Board.jpg|260px]]
| caption           = The fully-assembled C64 Reloaded MK-II PCB – all legacy chips have been installed
| developer         = Individual Computers (Jens Schönfeld)
| type              = Drop-in replacement motherboard
| first_released    = December 2016 (first pre-order run)
| latest_release    = Batch 2 production (2018)
| operating_voltage = Single 12 V DC input (2.1 mm barrel) – on-board SMPS generates +5 V, 9 VAC-equivalent and SID/VIC analogue rails
| application       = Commodore 64 / 64C replacement in new or original cases
}}

The '''C64 Reloaded MK-II''' (often written '''C64R MK2''') is a modern, factory-made Commodore 64 main-board produced by German hardware house '''Individual Computers'''.  
It retains full electrical compatibility with Commodore’s 8-bit chipset while replacing the fragile analogue power regulators, obsolete PLA and timing circuits with CPLD logic and efficient switch-mode converters.  
Unlike FPGA recreations such as the [[Ultimate 64 Motherboard|Ultimate 64]], the MK-II still uses ''original'' MOS custom chips supplied by the user.

==  📦 What’s in the box ==
* Finished four-layer PCB with every passive/logic part soldered and QC-tested.  
* Five professional ZIF-sockets for the legacy ICs:  
''' CPU (6510/8500)  
''' VIC-II video (6567/6569/8565/8562)  
''' Two CIA interface chips (6526/8521)  
''' One or two SID sound chips (6581/8580) – stereo is optional  
* Dual colour power LED, barrel-jack PSU lead and RF-shield stand-offs.

The buyer contributes only the vintage chips, keyboard, case and a 12 V notebook-style power brick.

==  🔑 Key features ==
; Universal video
: PAL '''and''' NTSC crystals are fitted; a CPLD-controlled PLL and software menu let you swap standards without moving jumpers.  
; Integrated PLA replacement  
: A Xilinx XC9500 CPLD implements the entire PLA logic with cycle-accurate timing.  
; Eight switchable Kernals  
: 512 kB flash stores the original CBM Kernal, JiffyDOS and six user images; a tiny push-button (or RESTORE-long-press) selects the active bank.  
; Modern power architecture  
: On-board DC-DC converters create cool-running +5 V and the 9 VAC-derived rails; the board therefore needs '''only one 12 V supply''' and tolerates 7-20 V input.  
; Dual-SID stereo mixer  
: Independent analogue rails for 6581 (12 V) and 8580 (9 V) – any combination is allowed, with software-selectable base addresses.  
; IEC fast-loader safe  
: Strong, ESD-protected bus drivers allow hot-plugging of 1541-II/1571 drives and modern SD-based devices.

A micro-USB service port exposes an '''I2C-driven configuration menu''' where clock speed, drive strength, video delay and SID mixing can be fine-tuned from a PC utility.

==  🛠️ Required donor chips ==
{| class="wikitable" style="text-align:center; width:70%"
! Socket !! Function !! Notes
|-
| U1 || 6510 / 8500 CPU || All speed grades supported
|-
| U2 & U3 || 6526 / 8521 CIA (×2) || Either NMOS or HMOS pair
|-
| U4 || 6567/6569 or 8562/8565 VIC-II || Auto-detects and sets clock
|-
| U5 / U6 || 6581 / 8580 SID (1 or 2) || Independent analogue rails
|}

==  ⚡ Power & regulations ==
* '''Input:''' 12 V DC @ ≈1 A via 2.1 mm barrel jack (centre-positive).  
* '''Rails generated:'''   
  +5 V   (3 A)  
  +9 V unregulated (SID 8580)  
  +12 V (SID 6581)  
  ~9 VAC square-wave for cassette motor & TOD clock.

The converters are >90 % efficient; board temperature stays below 35 °C in normal use – a marked improvement over the C64’s linear 7805/7812 regulators.

==  🎛️ Firmware / configuration ==
On first power-up the CPLD scans the sockets, identifies each chip revision and writes sane defaults to flash.  
Holding the '''MENU''' pushbutton during reset launches a ROM-resident setup program that lets the user:  

* select PAL (50 Hz) / NTSC (60 Hz) / Turbo (2 MHz VIC-off) modes  
* assign Kernal banks to the selector button  
* map SID #2 to \$D420 (Stereo IN) or \$D500 (compatible with SID FX)  
* adjust video phase to centre the image on HDMI up-scalers.

==  🛒 Availability & pricing ==
Two production runs have been sold exclusively through the Individual Computers web-store:

{| class="wikitable" style="width:75%; text-align:center"
! Batch !! Year !! Units !! Intro price (EUR) !! Status
|-
| 1 || 2016 || ≈ 600 || €199.90 || Sold-out
|-
| 2 || 2018 || ≈ 800 || €214.90 || Sold-out
|}

A third run has been teased but no firm date announced (as of Q1 2025).  
Second-hand prices on auction sites routinely exceed €300, especially for boards that include rare 6581R4AR SIDs.

==  🔧 Known quirks ==
* Very early boards shipped with a SID audio balance offset; a CPLD firmware update (v0.9-RC4 or later) fixes the issue.  
* The menu program requires a '''PS/2-level''' USB-TTL cable; generic 5 V serial adapters can harm the CPLD.  
* PAL-E VIC-II 6569R1 chips are *not* supported due to their uncommon timing.

==  📚 Further reading ==
* Individual Computers – C64 Reloaded MK-II press release (2016)
* “Building my C64 Reloaded MK2” – *AmigaLove* forum photo-essay, 2018 -10-15
* GRay Defender, “Commodore 64 MK2 Reloaded” – YouTube build log, 2020 ©

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