The developer Chris Fenton develops supercomputers professionally and is intensively involved with vector processor computers from Cray. As a fun project, he has now developed a Wristwatch based on a Cray CPU core and whose housing is in the style of the CrayC90 The watch is not really suitable for everyday use, but it is an impressive miniaturization of Cray technology.
The heart of the clock is a CMOD-A7 FPGA board from Diligent, which runs a completely rewritten core based on Cray’s vector processors. This is responsible for displaying the “Time” on a round OLED screen.
The core reaches a clock speed of 105 MHz, which is the speed of the CrayJ90 In order to be able to debug and maintain the CPU core better, Fenton changed some things at the microarchitecture level. For example, there is no longer any vector chaining.
OLED display instead of dome
The case of the watch is the same as the Cray C90 in a 25:1 ratio. Fenton chose the design primarily because the Cray C90 had a dome, which he could easily replace with the round display. In terms of speed, the watch is more like the Cray J90 than the Cray C90.
The CPU core shows a gravity simulation of Jupiter with its 63 moons. Each of the bodies shown interacts with all the others, and the calculations are carried out entirely on the clock. Fenton initially wrote the program in Python and simulated Cray vector instructions. He later translated the code into machine language.
Theoretically, you can even read the time from the simulation, but it is not entirely trivial or intuitive. The data for the ephemeris comes from NASA and always arrives at a certain time of day. Theoretically, you could enable the frames to be output in real time; if you then know the start time of the gravity simulation, you can determine the current time.
Watch should be complex and cumbersome
The fact that this is relatively complicated and time-consuming is something Fenton is keen to do. According to his own statement, he developed the Cray watch with the idea that its use should be as incomprehensible as possible. The watch can be worn on the wrist with a NATO strap, but due to its size, Fenton sees it more as an accessory on a desk.