Sega’s custom 1991 Sonic Mega CD BIOS resurfaces online
Sonic Team’s creative director received his very own SEGA CD BIOS as an office gift in 1991, nearly 35 years ago. This exact boot EPROM has now resurfaced online from a single dumped EPROM, with one logo and one revision string removed from the original retail version.
A BIOS image published for all
The Preservation Group Hidden Palace published this custom Mega CD BIOS, which was made exclusively for Sonic Team’s creative director at the time, Kazuyuki Hoshino, during his first year at Sega. A Discord contributor who goes by gageiro gets credit for discovering the BIOS. Hidden Palace took to X and stated:
“A really cool find from Discord member gageiro: A custom Mega CD BIOS made especially for Sonic Team’s creative director Kazuyuki Hoshino!”
Hidden Palace also tagged Kazuyuki Hoshino, who decided to share his side of the story from his time as a new member of the MEGA CD development team. He shared a few interesting details in an X post, stating:
“In 1991, I was a fresh new employee on the Mega CD dev team.
At the time, hardware-based rotation and scaling of graphics was something the Super Nintendo was known for. We finally made it happen on a SEGA system too, and I was so happy about it!
I was the only artist on the team, so I created the graphics needed for development. This test image was one of them.
Being the youngest on the team, my coworkers really looked after me. So they even made this awesome version just for me. Seeing this again after all these years brings back so many memories. I’m really grateful for those days and for the amazing people I got to work with.”
The original 1991 version of the SEGA CD plays a jingle and displays the MEGA-CD logo. Hoshino’s custom version instead displays a Sonic logo where the badge normally appears, along with the title text “SONIC: Hoshino’s Mega CD.”
The chip runs on retail version V1.11 firmware with two edits: a custom Sonic logo in place of the standard boot screen and a copyright line trimmed from “SEGA 1991 Ver1.11” to “SEGA 1991.”
However, the real mystery is how it turned up in Hidden Palace’s possession, as it is a custom-gifted EPROM handed from a junior artist to Hoshino. Even more perplexing is how the chip left SEGA’s hands and eventually ended up with a Discord user, with much of its provenance remaining unknown.
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