Editing Ultimate 64 Motherboard

{{Infobox computer
| name          = Ultimate 64
| image         = [[File:Ultimate64-board.jpg|260px|frameless]]
| caption       = Ultimate 64 Rev-A production PCB with optional dual-SID sockets
| developer     = Gideon Zweijtzer (Ultimate Products B.V.)
| manufacturer  = Ultimate Products B.V.<br />assembled in the Netherlands
| type          = FPGA-based replacement motherboard for the Commodore 64
| release_date  = December&nbsp;2018 (public launch)
| latest_release = Firmware '''1.46c''' (May 2024)
| price         = €239 (base) / €269 (Elite, 2024 list)
| cpu           = cycle-exact 6510 core inside an Altera Cyclone-IV FPGA @ 48 MHz system clock (internally down-clocked to 0.98/1.02 MHz for C64 compatibility)
| memory        = 64 KB main RAM (emulated),<br />16 MB SDRAM for Ultimate functions
| storage       = Integrated '''1541-Ultimate II+''' functionality:<br />• dual SD/µSD card slots<br />• two USB 2.0 type-A hosts<br />• tape-read/write buffers
| display       = HDMI 720 p (50 Hz PAL / 60 Hz NTSC) with optional CRT-style scalers;<br />composite & S-video on DIN 8 AV port
| sound         = Two SID sockets (6581/8580/Swinsid/ARMSid) with automatic 9 V/12 V selection,<br />FPGA “Ulti-SID” emulation, 48 kHz 16-bit stereo over HDMI & USB-audio
| networking    = 100 Mbit/s Ethernet (RJ-45), optional Wi-Fi via USB
| dimensions    = 403 × 100 mm (matches C64C short-board standoffs)
| weight        = 410 g (populated, without case)
| os            = Commodore BASIC 2.0 ROM + Ultimate 64 menu firmware
| compatibility = Commodore 64, Commodore 128 (C64 mode), most cartridges & IEC drives
| predecessor   = [[1541 Ultimate II+]] (cartridge)
| model         = Ultimate 64, Ultimate 64 Elite
}}
The '''Ultimate 64''' (commonly abbreviated '''U64''') is a modern, FPGA-based drop-in replacement for the Commodore 64 motherboard developed by Dutch engineer '''Gideon Zweijtzer''', creator of the 1541-Ultimate series.  Unlike software emulators, the U64 implements the complete C64 chipset (CPU, VIC-II, SID, CIAs, PLA, etc.) as gate-level clones inside a Cyclone-IV FPGA, delivering cycle-exact timing while adding contemporary amenities such as HDMI, Ethernet and solid-state mass-storage.

== Key features ==
* '''All-FPGA core''' – replaces every major MOS device, eliminating ageing silicon while preserving ~99.9 % software and demo compatibility, including tricky “cycle-tricks” and bad-line conditions.
* '''Integrated 1541-Ultimate II+''' – IEC drive emulation (D64/G64/TAP/T64/PRG), freezer, action-replay, REU (RAM Expansion Unit) up to 16 MB and GeoRAM, plus KERNAL cartridge injection and SID player.
* '''Digital video & audio''' – lag-free HDMI output at 720 p with optional scan-lines, border cropping and PAL/NTSC switching on-the-fly; 48 kHz 16-bit stereo mixes real SIDs with FPGA soft-SID.
* '''Dual-SID support''' – two physical sockets with automatic 9 V/12 V rail sensing; FPGA mixer allows true stereo separation and independent filter curves per chip.
* '''Network stack''' – 100 Mbit LAN for disk-image mounting over FTP/TFTP, firmware updates, IEC drive sharing and real-time clock synchronisation via NTP.
* '''Ultimate Command Interface''' – JSON‐RPC over USB or Ethernet for headless control and integration with PC front-ends.
* '''Silent & cool''' – the board draws ≈ 1.1 A @ 5 V; an optional 40 mm fan header is provided but rarely needed.

== Hardware overview ==
{| class="wikitable" style="text-align:center; width:70%;"
! Component !! Implementation !! Notes
|-
| CPU / PLA || Cyclone-IV EP4CE10F17C8N || 10 k LE FPGA (@ ~48 MHz master)
|-
| RAM || 16 MB 166 MHz SDRAM || shared by REU, GeoRAM, freezer snapshots
|-
| ROM || 2 × 1 Mbit SPI flash || holds multiple KERNALs & cartridge cores
|-
| Storage || µSD (front), SD (rear), 2×USB‐A || FAT32/exFAT up to 2 TB
|-
| Video || ADV7125 DAC + HDMI transmitter || PAL/NTSC S-video & composite preserved
|-
| Audio || TLV320AIC23B codec || 16-bit 48 kHz ADC for cassette in; DAC for soft-SID
|-
| I/O || RTL8211E Gig-Ethernet PHY, FT232H USB FIFO || network & USB mass-storage/front-panel control
|}

== Models and revisions ==
* '''Ultimate 64 (standard)''' – black PCB, single SID socket, no on-board RAM for cartridge emulation (relies on SDRAM).
* '''Ultimate 64 Elite''' – blue PCB, dual SID sockets, gold ENIG finish, additional fan header and improved audio output stage.
Both share the same FPGA bit-stream; differences are purely BOM-level.

== Firmware ==
Firmware images carry the prefix '''U64-<version>.bin''' and are flashed from the built-in Ultimate menu (F2) or via FTP.  Major branches:

{| class="wikitable" style="width:70%;"
! Branch !! Highlights
|-
| 1.4x (2022-) || HDMI low-lag scaler, new Soft-SID engine, EasyFlash 3 emulation, TC64-style turbo-CPU up to 48 MHz.
|-
| 1.3x (2020-2021) || REU page‐cross timing fixes, GeoRAM write-through, “Ulti-Pause” button mapping.
|-
| 1.2x (2019) || first public stable; added CRT composite sharpening and TAP write-back support.
|}

== Compatibility ==
The board fits in any Commodore 64 “bread-bin” or C64C case; all original ports retain their position.  Cartridge timing is cycle-accurate, so devices such as EasyFlash 3, Kung-Fu Flash, Tapecart, Ultimate II+ (cartridge), SuperCPU, REU 1764/1750, and RAMLink have been verified to boot.
Limitations:

* No analogue RF output (the TV modulator footprint is unused).  
* Turbo-CPU modes (>1 MHz) break raster IRQ stable code and some fast-loader drive hand-shakes.  
* Cassette motor control is emulated; certain fast-loaders that sample the motor waveform may fail.

== Reception ==
Hardware reviewers praised the '''crisp HDMI output''', silent operation and the convenience of having a full 1541-Ultimate inside the case. Some purists argue that FPGA SIDs—though vastly improved—still fall slightly short of certain analogue filter nuances of late-8580 silicon.

== See also ==
{{plainlist|
* [[1541 Ultimate II+]]
* [[PLA Replacement Options]]
* [[JiffyDOS Kernal Upgrade]]
}}

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