Sega Mega CD BIOS Files

These Mega CD BIOS files are needed to run Mega CD ISOs on emulators. The Japanese, European and American Mega CD BIOS files are included.
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	"CD Sonic the Hedgehog" AKA Sonic CD 510 Beta

The earliest Beta version of Sonic CD, featuring three incomplete levels. Most likely used for a press release. Dubbed as the 510 Beta due to its build date of 5/10/93.
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	Sonic CD 712 Beta

Very close to the finished version of Sonic CD, with only a few subtle differences. Dubbed as the 712 Beta due to its build date of 7/12/93.
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	Sonic CD 920 Beta

More of a pre-release rather than a Beta version of Sonic CD. It's basically US version of Sonic CD with the Japanese soundtrack. Dubbed as the 920 Beta due to its build date of 9/20/93.
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	Sonic CD (Japanese)

Released on September 23rd 1993, this was the first release of Sonic CD.
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	Sonic CD (European)

Released in October 1993, this was essentially the same as the Japanese version of Sonic CD, only converted to the PAL refresh rate of 50Hz.
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	Sonic CD (American)

Released on November 19th 1993, this version of Sonic CD had a different soundtrack to the Japanese and European versions of Sonic CD.
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