Ted Fried Builds "the World's Fastest CoCo" with the Motorola 6809-Emulating MCL6809
Compatible, in theory at least, with anything powered by Motorola's original, the MLC6809 can deliver up to an eightfold performance boost.
Vintage computing enthusiast Ted Fried has released the MCL6809, a drop-in replacement for the Motorola 6809E microprocessor — powered by a Teensy 4.1 microcontroller and providing, he says, cycle-exact emulation of the original chip.
"The simple C code runs both the 6809 emulation and controls the local bus interface to the motherboard," Fried explains of his creation. "The small PCB translates between the Teensy and MC6809E pinouts and provides a few voltage level shifters due to the fact that the Teensy IOs [Inputs/Outputs] are 3.3V and the motherboard IO’s are 5V."
The original Motorola 6809, designed by Terry Ritter and Joel Boney, launched in 1978 as a high-priced but powerful alternative to the popular Zilog Z80 and MOS Technology 6502.
Its cost, and a launch that put it head-to-head with early 16-bit processors, limited its success — but Motorola still found design wins in the Tandy TRS-80 Color Computer, the Dragon Data Dragon 32, Commodore's SuperPET, and the unusual vector-based Vectrex home console, among others.
For those who have one or more of the above, Fried's MCL6809 can act as a replacement for an original Motorola 6809 gone bad. Alternatively, it can be swapped in for an original to act as an upgrade — delivering, in Fried's testing, a helpful doubling of performance in a TRS-80 Color Computer, or up to an eightfold boost if you don't mind the resulting CoCo being "practically unusable."
This isn't the first time Fried has turned modern technology into a drop-in replacement for hard-to-find vintage chips: two years ago he unveiled the MLC86jr, an FPGA-powered upgrade for IBM's sluggish PCjr line; the MLC64 used a Teensy 4.1 board to perform similar magic in a Commodore 64; and the ML68+ used the same to replace the processor in an Apple Macintosh.
More unusually, Fried's MLC65+ acted as a downgrade to turn an Apple II into a working Apple-1 clone — while another Teensy-based project created the world's only Motorola 68000-powered IBM PC.
More information on the project is available on Fried's blog, while the source code and PCB design files have been published to GitHub under an open-source license.