Ultimate 64 Motherboard
 | |
| Ultimate 64 Rev-A production PCB with optional dual-SID sockets | |
| Specifications | |
|---|---|
| Developer | Gideon Zweijtzer (Ultimate Products B.V.) |
| Manufacturer | Ultimate Products B.V. assembled in the Netherlands |
| Type | FPGA-based replacement motherboard for the Commodore 64 |
| Released | December 2018 (public launch) |
| Intro 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), 16 MB SDRAM for Ultimate functions |
| Storage | Integrated 1541-Ultimate II+ functionality: • dual SD/µSD card slots • two USB 2.0 type-A hosts • tape-read/write buffers |
| Display | HDMI 720 p (50 Hz PAL / 60 Hz NTSC) with optional CRT-style scalers; composite & S-video on DIN 8 AV port |
| Sound | Two SID sockets (6581/8580/Swinsid/ARMSid) with automatic 9 V/12 V selection, FPGA “Ulti-SID” emulation, 48 kHz 16-bit stereo over HDMI & USB-audio |
| Dimensions | 403 × 100 mm (matches C64C short-board standoffs) |
| Weight | 410 g (populated, without case) |
| OS / Firmware | Commodore BASIC 2.0 ROM + Ultimate 64 menu firmware |
| Predecessor | 1541 Ultimate II+ (cartridge) |
| Model no. | 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
[edit | edit source]- 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
[edit | edit source]| 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
[edit | edit source]- 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
[edit | edit source]Firmware images carry the prefix U64-<version>.bin and are flashed from the built-in Ultimate menu (F2) or via FTP. Major branches:
| 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
[edit | edit source]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
[edit | edit source]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.