The Giga Drive Adaption

[Mike Berry]

Everyone must have heard by now, that Sonic 1 for the 3DS is nothing more than the Stock Sonic 1 rom that was reworked to support Stereoscopic 3D functions, as well as boost the overall performance with an increased frame rate of 120fps; but how was this even possible to do with a stock Mega Drive rom? And how would stereoscopic 3D work on the roms themselves?  The Giga Drive is an adaptive version of the original Mega Drive which supports, expands, or even allows:

・ Supports backward compatibility with Mega Drive games (Unmodified MDROMs will run normally without modification)

・Expanded VDP register for controlling expanded functionality included

・Expanded VRAM included

・Four extra background layers included

・Z-values can be set for each extra background or raster line

・Every sprite has a Z-value setting.

・VDP and Expanded VDP registers are memory-mapped and accessible

・VRAM and Expanded VRAM are memory-mapped and accessible

/*

* Memory Map

*

* $c00000 r/w VDP DATA

* $c00002 r/w VDP DATA

* $c00004 r/w VDP STATUS(read)/CTRL(write)

* $c00006 r/w VDP STATUS(read)/CTRL(write)

* $c00100-$c0012f -/w VDP REGS(write only)

* $c00130-$c0015f -/w EXT VDP REGS(write only)

* $c00200-$c0024f r/w VSRAM

* $c00300-$c0030f r/w DIPSW

* $d00000-$d0ffff r/w 64KB VRAM

* $d10000-$d1ffff r/w 64KB EXT VRAM

Although it doesn't seem like much, its still very interesting to say the least.

Read more at http://www.siliconera.com/2013/12/03/emulating-megadrive-3ds-isnt-easy-enter-3d-sonic-hedgehog/#SkrlYBctFlMFl4hw.99