Pseudonymous programmer and classic gaming fanatic “Grubby” has taken one thing written for the basic Zilog Z80 CPU and introduced it to a tool working on the fashionable eZ80 equal — which means now you can play the Sega Grasp System model of Sonic the Hedgehog 2 in your Texas Devices TI-84+ CE graphing calculator.
“It began in fall of 2022, after I was watching This Does Not Compute’s video on the historical past of graphing calculator gaming. Across the five-minute mark, he offhandedly mentions the type of processors TI’s graphing calculator line makes use of. Most of them use the [Zilog] Z80, the 89 and 92 use the [Motorola] M68K, and the Nspire line makes use of an Arm-based processor. That basically piqued my curiosity, since I already knew the processors that Sega’s retro sport consoles used: the Z80 for the Grasp System, and the M68K for the Genesis. The calcs have a grayscale display, however I wished to know if anybody ever tried porting a Sonic sport from the consoles to one of many calcs.”
Sonic the Hedgehog 2 is now playable on the TI-84+ CE calculator, due to its eZ80 CPU core. (📹: Grubby)
Regardless of utilizing, successfully, the identical CPUs, the reply turned out to be a shocking no: no one had but ported an authentic Sonic the Hedgehog sport to a Texas Devices calculator, although the Arm-base Nspire line might play them by means of fully-fledged console emulation. “That made me marvel if I used to be able to porting an present Sonic disassembly to a TI graphing calculator,” Grubby notes — and this time, the reply turned out to be sure.
Grubby picked the eight-bit model of Sega’s Sonic the Hedgehog 2, initially made for the Grasp System console, as the sport to port, and the TI-84+ CE because the machine to which it will be ported. Inside this calculator is an eZ80 core, a modernized variant of the Zilog Z80 CPU that drove the unique Grasp System — solely 24-bit quite than eight-bit.
Utilizing a disassembled model of Sonic 2, Grubby was in a position to make the required adjustments to accommodate the shift to some time new {hardware} platform — together with adapting the management system for the calculator’s keys, bringing the Grasp System’s six-bit 32-active-color palette to the system, recreate the unique cartridge’s mapper utilizing the calculator’s working system to simulate ROM banking, and deleting something to do with sound because the calculator lacks a speaker.
Two variations of the sport can be found, one slower however full and a sooner model with no bosses or gates. (📹: Grubby)
With a brand new customized renderer in place, the sport runs on the calculator with, admittedly, a considerably variable framerate relying on precisely what’s occurring on-screen. The venture additionally serves to display the compatibility between the unique Z80 and the eZ80, which comes following Zilog’s announcement that it was to discontinue manufacturing of the standalone Z80 and later Z180 processors — however go away the eZ80 alone, undoubtedly to TI’s reduction.
The total venture write-up is out there on Grubby’s weblog, whereas the venture supply code and a downloadable binary could be discovered on GitHub underneath an unspecified license.
