Ultimate 64 Motherboard
| |
| Caption | Ultimate 64 board, labelled V1.4 |
|---|---|
| Type | FPGA-based replacement motherboard |
| Designer | Gideon Zweijtzer |
| Manufacturer | Ultimate Products (ultimate64.com) |
| First released | Unknown |
| Latest revision | — |
| Operating voltage | — |
| Layers / PCB | — |
| Compatibility | Commodore 64 |
| Features | HDMI 576p50 output, Ethernet, three USB 2.0 ports, two SID sockets, turbo mode to 48 MHz (64 MHz on the Elite-II) |
| Model No. | Ultimate 64, Ultimate 64 Elite, Ultimate 64 Elite-II |
The Ultimate 64 (U64) is a replacement motherboard for the Commodore 64 that implements the machine in an FPGA. It was developed by Gideon Zweijtzer, the designer of the 1541 Ultimate cartridges, and runs the same Ultimate firmware and menu as the Ultimate-II+ cartridge. The board keeps the original tape, cartridge, audio/video and serial ports and adds HDMI, Ethernet and USB.[1][2]
Models and availability
[edit | edit source]On 1 October 2026 the ultimate64.com shop listed three Ultimate 64 items, all out of stock:[2]
| Product | Price |
|---|---|
| Ultimate-64-Elite | €248.95 |
| Ultimate 64 Elite-II | €248.99 |
| U64 UserPort Adapter, with 9 V AC | €9.98 |
The shop's home page says the Elite-II "black short boards" are sold out and that Commodore has taken over sales of its own version of the board. It also notes that the shop is run by one person and usually ships once a week.[2]
Video output
[edit | edit source]The HDMI output on the PAL version is 720 x 576 at 50 Hz (576p50), a standard CEA-861 mode with its timing slightly modified to match a C64. There is no frame buffer, so the board adds no frame delay; any lag comes from the display, and Gideon records one 4K screen that resampled the output to 30 Hz. When HDMI is in use, the C64 display connector is driven as well.[1]
Turbo mode
[edit | edit source]The CPU and memory subsystem run at 48 MHz on the Ultimate 64 and 64 MHz on the Elite-II. The turbo setting does not change that clock; it sets how many of the available time slots go to the CPU, and the VIC still takes the cycles it needs.[1]
Selectable CPU speeds:[1]
- Ultimate 64: 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 20, 24, 32, 40 and 48 MHz.
- Elite-II: 1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 20, 24, 32, 40, 48 and 64 MHz.
Badline timing can be turned off to give the CPU more cycles, but the setting does not change the BA signal on the cartridge port. Accesses to the cartridge port, which always run at 1 MHz, still meet the badline limits, and so do accesses to the SID registers when the physical SID sockets are enabled.[1]
Turbo control registers
[edit | edit source]The registers are available only when the turbo mode selector in the menu allows them:[1]
| Address | Function | Available when |
|---|---|---|
| $D030 (53296) | Turbo Enable Bit. Write 0 for 1 MHz with badlines, 1 to use the menu settings. Read 0 = turbo off, 1 = turbo on. | Selector set to "Turbo Enable Bit"; otherwise reads $FF |
| $D031 (53297) | U64 Turbo Control. Bits 0-3 CPU speed index; bit 7 badline timing (0 enabled, 1 disabled). | Selector set to "U64 Turbo Registers" or "Turbo Enable Bit"; otherwise reads $FF |
| $D07A (53370) | SuperCPU-compatible software speed select, normal. Write only. | As $D031 |
| $D07B (53371) | SuperCPU-compatible software speed select, turbo. Write only. | As $D031 |
| $D0BC (53436) | SuperCPU mode detect. Read only. | When separately enabled |
See also SuperCPU and Turbo Accelerators.
SID-TAP header
[edit | edit source]An 8-pin header brings out the analogue signals of the installed SIDs before the board's own processing. A 3.5 mm jack can be wired to the SID OUT pins as a line out; the SID IN pins give a line in, which Gideon notes has not been functionally verified.[1]
| Function | Pin | Pin | Function |
|---|---|---|---|
| SID 2 OUT | 1 | 2 | Ground |
| Ground | 3 | 4 | SID 2 IN |
| Ground | 5 | 6 | SID 1 IN |
| SID 1 OUT | 7 | 8 | Ground |
USB and network
[edit | edit source]There are three USB 2.0 ports, two at the back and one on the inner side of the board; USB 3 is not supported. USB 2.0 hubs work, and powered hubs are recommended; USB 1.1 hubs do not work. The Ethernet port shows as Net0 in the Ultimate menu, with a Network Settings menu for DHCP or a static address. It is not RR-Net compatible.[1]
Firmware
[edit | edit source]The firmware and the FPGA core carry separate version numbers: firmware 3.10 shipped with core 1.41 and 3.10i with core 1.42. Firmware 3.15 added Ultimate 64-II hardware support, a machine-code monitor, a REST API, an FTP client and a renewed software IEC subsystem.[1]
Not in the documentation
[edit | edit source]Gideon's documentation and the ultimate64.com shop do not give the FPGA part number, the RAM fitted, the board dimensions, the weight or the current draw. Read the markings on the board itself.
Related pages
[edit | edit source]- C64 Reloaded MK2
- SuperCPU and Turbo Accelerators
- PLA Replacement Options
- JiffyDOS Kernal Upgrade
- Commodore 64
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Gideon Zweijtzer, 1541 Ultimate-II(+) and Ultimate-64 Documentation (retrieved 2026-10-01): "Ultimate-64 Documentation" landing page; "HDMI port"; "Turbo mode settings"; "SID-TAP header"; "USB ports"; "Ethernet port"; "Firmware".
- ↑ 2.0 2.1 2.2 Ultimate Products, ultimate64.com home page and "Ultimate 64 Main Boards" (retrieved 2026-10-01).