ProDOS volumes
The IIc board is 128 MB, split across four ProDOS drives. The IIc Plus board is sold in 128 MB and 256 MB.
Apple IIc · IIc Plus
Internal storage that feels like it was always there
MegaFlash, designed by Thomas Fok, is an internal storage device for Apple IIc and IIc Plus computers—multiple ProDOS volumes, a 256 kB RAM disk, Wi‑Fi transfers, network time sync, Uthernet II emulation, and a full control panel—built around a Raspberry Pi Pico 2 W.
What you get
RAM & ROM disks
256 kB RAM disk on the Pico 2 W, plus a ROM disk for disaster recovery when you need a known-good boot path.
Slinky & boot menu
256kB Slinky emulation on stock IIc firmware, and a boot menu in the spirit of ROM4X/5X.
Control panel
Configure and manage the device from a dedicated control panel stored in Pico flash—no cramming everything into Apple ROM.
Time & networking
Real-time clock with a ProDOS driver, NTP sync over Wi‑Fi, TFTP for ProDOS images, and Uthernet II (W5100) emulation in slot 4.
Serial & extras
XModem over USB serial, an FPU for Applesoft BASIC, and fixes for System ROM and Applesoft quirks.
Boards
Two red boards. One mounts on the CPU socket in an Apple IIc. The other is built for the Apple IIc Plus, and can also run in an A2S4100 with the enabler kit.
Apple IIc
CPU-socket board for the A2S4000 and A2S4100. 128 MB. The system ROM replacement is included.
Apple IIc Plus
A separate board for the IIc Plus, in 128 MB and 256 MB. Either size can also be used in an A2S4100 with the enabler kit.
A2S4100 enabler kit
Connects address lines A2 and A3 to an IIc Plus MegaFlash so it can run in an A2S4100. That link is what turns on Uthernet II support, and other features still in development.
Requirements
Compatible systems
Apple IIc (A2S4000 or A2S4100) with the IIc board, or Apple IIc Plus with the IIc Plus board. An A2S4100 can use an IIc Plus board when the enabler kit is fitted. The system ROM replacement is provided.
Hardware snapshot
Raspberry Pi Pico 2 W (RP2350), Winbond 25Q01 NOR flash, GAL16V8 for decode, and 5V–3.3V level shifting. The 1.2 firmware is Pico 2 W only. Schematics are in the repository.
Development firmware
Current development is the 1.2 series for the Pico 2 W. The latest build is
v1.2.5-eo
(7 October 2026). Flash megaflash-pico2.uf2 from that release. The RAM disk is 256 kB in this
series so Uthernet II emulation has room to run.
Uthernet II
The Uthernet II is an Apple II Ethernet card. MegaFlash emulates that card and puts it on the Pico’s Wi‑Fi. MACRAW passes whole Ethernet frames to the Apple, which is how stacks such as Contiki and ip65 talk to the network. Socket mode lets the card handle TCP itself, so the Apple does less of the packet work. UDP stays on the MACRAW path. Performance tuning for both modes is still in progress.
Contiki
Contiki uses source port 1026 by default. Modern firewalls tend to block traffic from that port. MegaFlash shifts the port number so those connections get through.
WebTools disk
webtools.po ships with the v1.2.4-eo release. The v1.2.5-eo firmware archive does not include a newer copy of this disk. Some of the programs have been patched to work with MegaFlash.
- Contiki browser
- Contiki wget
- Contiki web server
- IP65 Telnet
- ADTPro over Ethernet
- A2osX Uthernet II driver, with install notes
We developed a new Uthernet II driver for A2osX so the operating system can use MegaFlash’s emulation.
Documentation
The project README, Pico firmware notes, and API docs live on GitHub. There is also a user guide (PDF) for deeper setup and usage detail.
Open the repository