C64 storage in 2026: SD2IEC, Pi1541, Kung Fu Flash and the Ultimate range

This review is based on the projects' own documentation and on vendors' listings read on 26 October 2026, not on hands-on testing. RetroMake has not used these devices for this piece, the compatibility statements below are their makers' claims, and there is no star rating for that reason.

A Commodore 1541 is a computer in its own right. The Pi1541 author describes a CPU, ROM, RAM and interface chips alongside the mechanism, and C64-Wiki names them: a 6502 processor and two 6522 interface chips. Fast loaders exploit that by uploading their own code to the drive. Every modern replacement makes a choice about that code. It can run it, cycle by cycle; it can recognise a known loader and imitate it; or it can bypass the drive and redirect the C64's own load routines. The choice decides what will load.

SD2IEC

The sd2iec firmware, written by Ingo Korb and released under the GPL version 2, connects SD and other cards to the Commodore serial bus. Its README describes the result as "a 1541 with a modern storage medium instead of disks" and claims good DOS and file-level compatibility with Commodore drives, for PRG files and D64, D71, D81 and DNP images. Then comes the limit: unless specifically noted, anything that tries to execute code on the 1541 will not work, "this includes every software fastloader". The project's download page puts it more bluntly: sd2iec is not a floppy emulator.

The README lists the exceptions it recognises: Turbodisk, the Final Cartridge III, Action Replay 6, Dreamload, ULoad Model 3, the Epyx FastLoad cartridge, GEOS and Wheels, and a few individual games, among them Maniac Mansion (cracked versions only, because the original's copy protection check is not supported), Zak McKracken and Sam's Journey. It also speaks the JiffyDOS protocol. The Pi1541 author describes the method from the other side: SD2IEC guesses a fast loader from the code sent to it and simulates the communication, so only a small number of popular loaders are supported.

Vendors describe the same hardware differently. Protovision tells buyers of its cableless model that an SD2IEC is "a little less compatible" than a 1541 Ultimate cartridge with multiload programs; phol-labs calls its cableless unit a "1541 Disk Drive Emulator". Protovision's and AMI64's units take their power from the cassette port, while TFW8B also sells a version powered from the user port.

Pi1541

Pi1541, written by Stephen White according to C64-Wiki, is free software under the GPL version 3 that turns a Raspberry Pi 0, 0-2, 3A+, 3B or 3B+ into "a real-time, cycle exact, Commodore 1541 disk drive emulator". It emulates the drive's 6502 and both 6522s, so it runs whatever code a loader sends. Its author says that supports "a vast range of fast loaders (games and demo scene) even copy protected originals". It reads D64, D81, G64, NIB and NBZ images, writes only D64 and G64, and has emulated the 1581 since version 1.13 (1.22 on the Pi Zero). The owner supplies a 1541 ROM image.

The Pi's inputs tolerate only 3.3 V, so the interface converts levels, and a 7406-based design is needed when other devices share the serial bus. The author warns that unbranded hex inverters can stop some disk images from working. Version 1.24, released on 23 January 2021, is still the latest, and the author calls a version for the Pi 4 or Pi 5 unlikely. The software is free, and he asks people who buy ready-made hardware to consider donating, noting that others are profiting from his work.

Kung Fu Flash

Kim Jorgensen's Kung Fu Flash is a cartridge, not a drive. Its project has moved from GitHub to Codeberg, where version 1.55 was released on 31 May 2026. It emulates cartridges, from generic 8K and 16K images to the Action Replay, Final Cartridge III, Super Snapshot 5, Epyx FastLoad and EasyFlash, and it loads PRG and T64 files and opens D64, D71 and D81 images.

The README is frank about the disk side. Its drive emulation uses KERNAL vectors and "will not work with fast loaders or software that uses direct hardware access which a lot of games does". REL files are not supported, and only a subset of DOS commands is.

It is a software-defined cartridge: a microcontroller imitates the cartridge hardware in software. The README warns that the C64 bus timing is in places "very close to the limit", and that a particular machine may need a phi2 offset adjustment or may not work correctly at all. It supports PAL and NTSC C64s and the C128.

Ultimate-II+L

Gideon Zweijtzer's Ultimate-II+L is the Lattice FPGA version of the Ultimate-II+ cartridge. The product page claims full, cycle-accurate emulation of two drives, each a 1541, 1571 or 1581, using D64, D71, D81, G64 and G71 images on USB storage. The documentation says the emulated 1541 "acts exactly like a real drive" and is not any faster or slower than one, and that since firmware 3.10 each drive can switch between 1541, 1571 and 1581 modes; alternative drive ROMs such as JiffyDOS can be installed. The same cartridge emulates the Final Cartridge III, Action Replay, Retro Replay, Super Snapshot, EasyFlash and Epyx FastLoad, adds a 1750/1764 REU of up to 16 MB, and handles tape images through an accessory cable. It has three USB ports and a 100 Mbps Ethernet port.

Ultimate 64 Elite-II

The Elite-II is the same idea at full size: an FPGA implementation of the entire C64, with the Ultimate-II+ built in, on a board the size of a short C64C board, 390 by 135 mm. It has HDMI, USB and Ethernet beside the original ports, and it is powered from USB-C, so no power supply is included. For an existing C64 it is a replacement motherboard rather than a storage add-on. Its maker's shop lists it as sold out and says that Commodore has taken over sales of its own version of the board.

Prices on 26 October 2026

Protovision's price carries no sales tax under section 19 of the German VAT act. Amiga-shop.net's includes 19 percent VAT.

The Kung Fu Flash bundles at amiga-shop.net and Ultimate MiSTer both include a 16 GB microSD card, and the Tindie listing, from AmericanRetro.shop, names firmware 1.48 in its title. The AMI64 unit comes with an 8 GB card, and TFW8B's range depends on the connector and options chosen.

Ultimate64.com's own pages disagree with each other: every one of the nine Ultimate-II+L colours showed Back Order, while the shop's front page said U2+L boards were in stock and that new orders include the WiFi module. The shop also warns that one person runs it alongside a full-time job and usually ships once a week.

Which one fits

The documentation draws the lines clearly. For PRG files and software that loads through the KERNAL, the cheap options cover it: an SD2IEC handles DOS-level loading plus its list of recognised fast loaders, and Kung Fu Flash adds cartridge emulation but loads disk images only through the KERNAL. For original disks, demos and anything with a custom loader or copy protection, the makers point to cycle-exact drive emulation. Pi1541 is the inexpensive route, provided the owner is content with a project whose last release is from 2021. The Ultimate-II+L puts drives, cartridges and an REU in one cartridge for about six times the price of the cheapest SD2IEC listed above, when it can be ordered. The Elite-II replaces the computer and is, for now, out of stock at its maker.