This Clever Clock Port Adapter Marries an Amiga 1200 with a Raspberry Pi for Easy Wi-Fi Networking
Sharing just 64kB of SRAM between an Amiga and a Raspberry Pi, this clever FPGA board provides a way to get a classic computer back online.
Niklas Ekström has released an add-on board for classic Commodore Amiga 1200 computers, designed to interface with a modern Raspberry Pi through the system's clock port — offering the ability to connect the Amiga to Wi-Fi networks without tying up the PCMCIA slot.
"This interface has a small 64kB SRAM [Static RAM] memory that is shared between an Amiga and a Raspberry Pi," Ekström explains of his board design. "The Amiga connects to the interface through the clock port." That's worth noting: the Amiga's clock port was originally designed, as the name implies, to accept a real-time clock with or without memory expansion — but was later repurposed as a general accessory port, which is how Ekström uses it.
The compact adapter board connects to the Amiga 1200's clock port and acts as a bridge between the original Amiga hardware and a modern Raspberry Pi single-board computer (SBC). The two devices never talk directly, however: Instead they both have access to a shared 64kB memory chip, providing a means of communication between the two.
"Either side, the Amiga or the Pi, can read from and write to the SRAM," Ekström explains. "The interface is eight bits wide, meaning that each access reads or writes one byte. The interface is symmetric between the sides."
That simple 64kB shared memory is enough to allow the Amiga to take advantage of the hardware available on the Raspberry Pi — including its Wi-Fi radio. "The A314 software has been adapted to this interface," Ekström writes, "so that it is possible to run services such as a314fs and the SANA-II network driver." Using the clock port in this way, it's possible to connect an Amiga 1200 — or other Amiga model, if fitted with a clock port adapter — to a network without tying up the precious PCMCIA slot at the left-hand side and fit an increasingly hard-to-find period-appropriate Wi-Fi card.
Ekström isn't the only one to think about putting modern hardware in vintage systems as a coprocessor or accelerator: Back in April 2021 we tested Claude Schwarz' low-cost PiStorm accelerator for the Commodore Amiga, designed to replace the stock CPU with a Raspberry Pi 3 Model A+ running an emulator; more recently we've seen Ted Fried using a Teensy 4.1 microcontroller board to accelerate a Commodore 64 and a field-programmable gate array (FPGA) to boost an IBM PCjr.
Design files and source code for the adapter are available on Ekström's GitHub repository, under the reciprocal GNU General Public License 3.
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