Editing SuperCPU and Turbo Accelerators

{{Infobox hardware
| name           = SuperCPU and turbo accelerators for the Commodore 64/128
| image          = [[File:CMD_SuperCPU64.jpg|250px]]
| caption        = The Creative Micro Designs SuperCPU
| type           = Cartridge-port CPU accelerators
| manufacturer   = Creative Micro Designs and others
| application    = Commodore 64, 64C, SX-64 and Commodore 128 in 64 mode
}}
<templatestyles src="Template:StyledTable/styles.css" />

A '''turbo accelerator''' replaces or bypasses the Commodore 64's 1 MHz 6510 with a faster processor while keeping the rest of the machine working. The best known is Creative Micro Designs' '''SuperCPU'''.

'''This page carries only figures that can be checked against a maker's documentation or a community reference that mirrors it.'''<ref name="c64wiki">''SuperCPU'', C64-Wiki, https://www.c64-wiki.com/wiki/SuperCPU . Community reference. Source for the manufacturer, release and discontinuation years, release price, processor, clock, support-chip type, on-card RAM and ROM, expansion options, the v1-to-v2 CPLD change, and the SuperCPU register map at $D074–$D0BC with system and user RAM at $D200–$D3FF. It also lists the other accelerators named below.</ref><ref name="u64">Gideon Zweijtzer, ''Ultimate Documentation'' — Turbo mode settings, https://1541u-documentation.readthedocs.io/ . Source for the Ultimate 64's SuperCPU-compatible registers at $D07A, $D07B and $D0BC, for the 48 MHz and 64 MHz subsystem clocks and CPU speed indices, and for the statement that disabling badline timing does not affect the BA signal at the cartridge port.</ref>

== The SuperCPU ==

{| class="wikitable styled-table" style="width:75%; text-align:left;"
|+'''CMD SuperCPU'''
! !! 
|-
| Manufacturer || Creative Micro Designs
|-
| Released || 1996
|-
| Discontinued || 2001
|-
| Release price || US$199
|-
| Processor || WDC 65C816S
|-
| Clock || 20 MHz
|-
| Opcodes || Documented 6510 opcodes only
|-
| Support chip || Altera CPLD
|-
| On-card RAM || 128 KB SRAM
|-
| ROM || 64 KB SuperCPU DOS
|-
| Expansion || Cartridge pass-through, SuperRAM Card (1–16 MB), "Rocket Socket" header
|-
| Installation || External, cartridge port
|}
<ref name="c64wiki" />

'''v1 against v2.''' The first SuperCPU was released with an Altera CPLD too small to hold all the compatibility logic CMD wanted, and it was buggy as a result. The second version fitted a higher-capacity CPLD and generally solved the problem. If you are buying one, that is the difference that matters.<ref name="c64wiki" />

=== Register map ===

The SuperCPU is controlled and detected through registers in the $D0xx space. This matters beyond the SuperCPU itself, because later hardware imitates it.<ref name="c64wiki" />

{| class="wikitable styled-table" style="width:90%; text-align:left;"
|+'''SuperCPU registers'''
! Address !! Purpose
|-
| $D074 (53364) || VIC bank 2 / GEOS optimisation (mirror $8000–$BFFF)
|-
| $D075 (53365) || VIC bank 1 optimisation (mirror $4000–$7FFF)
|-
| $D076 (53366) || BASIC optimisation (mirror $0400–$07FF)
|-
| $D077 (53367) || No optimisation — mirror all memory (v1 default)
|-
| $D07A (53370) || Software speed select — normal
|-
| $D07B (53371) || Software speed select — turbo (20 MHz)
|-
| $D07E / $D07F || Hardware register enable / disable
|-
| $D0B0 (53424) || SuperCPU mode detect register
|-
| $D0B3 (53427) || Enhanced optimisation register (v2 only)
|-
| $D0B4 (53428) || Optimisation mode flags (v1 and v2)
|-
| $D0B5 (53429) || JiffyDOS switch flag / CPU speed switch flag
|-
| $D0B6 (53430) || Processor emulation mode flag (v1 only)
|-
| $D0B8 (53432) || Software speed flag / master speed flag
|-
| $D0BC (53436) || DOS extension mode flag / RAMLink hardware registers flag
|-
| $D200–$D2FF || System RAM
|-
| $D300–$D3FF || User RAM, available to user programs
|}

== The SuperCPU's afterlife ==

The register interface outlived the hardware. The '''[[Ultimate 64 Motherboard|Ultimate 64]]''' implements '''SuperCPU-compatible''' software speed-select registers at '''$D07A''' and '''$D07B''' and a '''SuperCPU detect register at $D0BC''', so software written for a SuperCPU can find and drive its turbo.<ref name="u64" />

The U64 is also worth reading for one lesson that applies to every accelerator: on that board, disabling badline timing gives the CPU more slots but '''does not change the BA signal at the cartridge port''', so anything reaching an external device — or a real SID in a socket — is still throttled by badlines. Accelerating the processor never accelerates the bus it has to share.<ref name="u64" />

== Other accelerators ==

The following are recorded as C64/C128 CPU accelerators:<ref name="c64wiki" />

* '''Turbo Process'''
* '''Turbo Master CPU'''
* '''Flash 8'''
* '''Turbo Chameleon 64'''
* '''F7 Turbo Card'''
* '''Turbo Demo Card (TDC)'''

'''This wiki has not verified the processor, clock, RAM fit or release date of any of these against its maker's documentation''', and does not state them. Specification tables for these machines circulate widely and contradict each other; several published comparisons attribute one product's parts to another.

'''The Turbo Chameleon 64 is end-of-life at Individual Computers''' — its wiki page is filed under their EOL category — so do not treat it as a current purchase.<ref name="icomp">Individual Computers, ''Chameleon'', https://wiki.icomp.de/wiki/Chameleon . Filed under the manufacturer's '''EOL''' category.</ref>

== The modern route to a fast 64 ==

If the object is speed rather than period hardware, the practical options today are FPGA boards rather than cartridges:

* '''[[Ultimate 64 Motherboard|Ultimate 64 and Ultimate 64 Elite-II]]''' — up to 48 MHz and 64 MHz respectively, with SuperCPU-compatible control registers.<ref name="u64" />
* '''Commodore 64 Ultimate''' — the board Commodore now sells, built on an AMD Xilinx '''Artix-7''' FPGA with 128 MB of DDR2 and 16 MB of flash. Pre-orders opened at '''US$299.99''' for the base machine, with a Starlight edition at $349 and a Founders edition at $499, and shipping was announced for October 2025. Ultimate64.com states that Commodore has taken over sales of their version of the Elite-II board.<ref name="c64u">Announcement coverage of the Commodore 64 Ultimate, e.g. Tom's Hardware, https://www.tomshardware.com/video-games/retro-gaming/the-commodore-64-ultimate-computer-is-the-companys-first-hardware-release-in-over-30-years-pre-orders-start-at-usd299 . Source for the Artix-7 FPGA, 128 MB DDR2, 16 MB flash, the three editions and their launch prices, and the announced October 2025 shipping date. Prices are launch figures, not current ones.</ref><ref name="u64shop">Ultimate Products B.V., https://ultimate64.com/ — front-page notice that the Ultimate 64 Elite-II black short boards are sold out and that Commodore has taken over the sales of their version of this board. Read September 2026.</ref>

== Power ==

Any cartridge-port accelerator adds load to the C64's +5 V rail, which the original Commodore supplies were never generous about. If you are running one on a period brick, read [[Commodore 64 Power-Supply Protector (C64 Saver)]] first — an ageing supply that has begun to drift high will take the accelerator with it.

'''This wiki has no measured current figure for any accelerator on this page.''' Measure yours rather than trusting a published one.

== Related pages ==
* [[Ultimate 64 Motherboard]]
* [[C64 Reloaded MK2]]
* [[Commodore 64 Power-Supply Protector (C64 Saver)]]
* [[PLA Replacement Options]]
* [[JiffyDOS Kernal Upgrade]]

== References ==
<references />

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