Adafruit Shows Off the RP2350 Fruit Jam's Emulation Prowess as a Pico-Mac-Powered Macintosh 128K

Adafruit has shown off the ability of its upcoming single-board computer, the RP2350 Fruit Jam, to emulate classic machine — celebrating "Marchintosh" with an emulated Apple Macintosh with upgraded RAM.

"One of my favorite computers that I grew up with was the Mac 512k," Adafruit's Limor "LadyAda" Fried explains. "This is running Pico-Mac, but what's cool about this is that Jeff Epler spent the week porting it to use HSTX [High-Speed Transmission]. So this is on the [Raspberry Pi] RP2350, and it uses the DVI output so you don't need VGA connectors or resistors or whatever."

The original Apple Macintosh launched as a successor to the Apple Lisa in 1984, the brainchild of Jef Raskin. The original Macintosh was based on a Motorola 68000 processor, featured 128kB of RAM, and used an integrated 9" CRT black and white display in a housing with a 3.5" floppy drive, connected to a compact keyboard and iconic one-button mouse. The version Fried remembers using is an upgraded version, launched later in 1984 as the Macintosh 512K — the original undergoing a rename to the Macintosh 128K to differentiate the two.

The RP2350 Fruit Jam, meanwhile, is something newer: a single-board computer inspired by the Programming Club Network (PCN) IchigoJam, powered by Raspberry Pi's latest RP2350 dual-dual-core microcontroller. With two Arm Cortex-M33 cores and two Hazard3 RISC-V cores, any two of which can be chosen on boot, and 520kB of static RAM, the RP2350 is technically more powerful than the processor that drove the Macintosh 128K — giving it the ability to emulate one, among other systems of a similar era.

In Adafruit's demo, the board is shown emulating an original Macintosh 128K but with a RAM upgrade to 384kB — the 520kB available on the RP2350 being too little to fit both the emulator and serve the 512kB of RAM required to emulate a Macintosh 512K. The display output comes through the RP2350's new HSTX port, which can be used to drive a DVI video signal compatible with HDMI monitors and TVs without tying up any of the CPU cores or the programmable input/output (PIO) blocks.

But how long will it be before you can have your own Apple-emulating RP2350 Fruit Jam? "Fruit Jam is still a work in progress," the company admits, "[and] we have to revise the PCB to fix some errors." Interested parties can sign up on the company's store to be notified when boards are available to buy.