Reverse engineering Yamaha’s Classic YM21280 OPS Chip — the Heart of the DX7 Synth @kenshirriff @Hacksterio
Noted computer historian and reverse engineer Ken Shirriff has turned his attentions to the Yamaha DX7 digital synth from the 1980s — reverse engineering the operation of its YM21280 OPS operator chip from high-resolution die imagery.
“The Yamaha DX7 digital synthesizer was released in 1983 and became ‘one of the most important advances in the history of modern popular music,'” Shirriff writes. “It defined the sound of 1980s pop music, used by bands from A-ha and Michael Jackson to Dolly Parton and Whitney Houston. The DX7’s electric piano sound can be heard in over 40% of 1986’s top hits.”
To dive deeper into exactly how the device worked, Shirriff removed the metal cover from a YM21280 OPS chip — the so-called “operator” chip, one of two key custom chips in the synth alongside the YM21290 EGS “envelope” chip — and took over a hundred images of the silicon through a microscope. By compositing these, Shirriff created a high-resolution image of the circuitry — offering clues at how the 64-pin quad in-line package (QIP) did what it did.
“The shift registers are the largest blocks of the chip, especially the phase shift registers in the upper left,” Shirriff explains of his discoveries. “ROMs are the second-largest blocks, especially the sine ROM and the two identical exponential ROMs. Adders provide most of the logic circuitry; there isn’t much ‘random’ logic compared to a processor chip, for instance. The chip has several bit shifters that shift a numeric value, multiplying or dividing it by a power of two.”
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7:30pm ET! To join, head over to YouTube and check out the show’s live chat and our Discord!
Python for Microcontrollers – Adafruit Daily — Python on Microcontrollers Newsletter: CircuitPython Comes to the ESP32-P4, Emulating Arm on RISC-V, and Much More! #CircuitPython #Python #micropython @ThePSF @Raspberry_Pi
EYE on NPI – Adafruit Daily — EYE on NPI Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey
Thank you for writing about my DX7 article. I should point out that the chip is the YM21280, not the TM21280. I want to make sure people don’t get confused and start using the wrong name.
Thank you for writing about my DX7 article. I should point out that the chip is the YM21280, not the TM21280. I want to make sure people don’t get confused and start using the wrong name.
Thanks Ken & sorry, I used the Hackster article quite a bit and I should have checked more – caffeine deprived. Corrected. Great work!