At first, Mirage was anything but a traditional emulator--the video consisted of squares on a black background (showing where sprites would be) and pages of debugging information. It did not run in real-time, there was no controller interface, no SPC700 chip emulation (required for sound), a text-based user interface. It was meant for programmers and used for writing code. Final testing was done on a real Super Fami
unit.
However, over time, the Mirage project got more advanced. Of course, bugfix after bugfix was added, patching the code to make sure its output matched that of a real Super Fami. A team working on some tricky graphical effects added the first major patch, a separate window (originally forced onto a second monitor) which would render a virtual SNES screen. This process took several seconds on our original hardware--one could watch the screen slowly draw from top to bottom--but it worked, and it was more accurate than most of the emulators you see today. A second team optimized the code, and combined with computer upgrades around the Nintendo offices, this let Mirage run in pseudo-realtime, although it was a fraction of the speed of a real Super Famicom.
It soon became common to test games on Mirage more and more extensively. Developers found that the time needed to load their code from Mirage into the testing units (up to a minute for large games) was excessive, when with a click of the mouse they were able to immediately see the game running within Mirage. Of course, there were a lot of limitations, and nobody would argue that Mirage could replace a real unit, but it was a start.
This is where the story gets interesting. In late 1996, a high-level executive (who will remain anonymous) at Nintendo came to the Rare labs one day, and saw a coder working on his game using Mirage. (Trivia tidbit: Yes, Rare has many of its development labs within Nintendo of America headquarters nowadays--they were always in bed together, now more recently they've even shacked up. Diddy Kong Racing--shudder.) By
now, computer hardware had advanced to allow Mirage to run at playable speeds on this guy's average desktop hardware. Suddenly the potential struck him--Super Nintendo games on household PCs! Obviously there's a market.
Nintendo of Japan shrugged off the idea, but they always have--NOJ is known for passing over potentially valuable markets, and focusing on selling elaborate junk to young children (Virtual Boy, anyone?). On the other hand, Nintendo 64 has not been the blockbuster that was hoped for in the US market; obviously the higher-ups overestimated the market for $79 games designed for kids when competing systems sell their games for $39. Regardless, the project Silhouette was spun off from Mirage in an attempt to broaden Nintendo's market to PC owners, especially those who liked SNES software. Silhouette had two main developers, myself being one of them; the Mirage team also worked on large portions. Silhouette was designed to be a subset of Mirage; its purpose was to play games, and be as optimized as possible for today's computer hardware, but be as accurate as possible. No debugging windows, no test modes, no compiler--just the emulated hardware, with the best possible gaming experience. Every attempt was made in Silhouette's course of development to obtain speed without sacrificing compatibility.
In many cases Silhouette was forced to expand to include features that Mirage did not cope with. For example, Mirage had no sound support whatsoever--Silhouette includes a full SPC700 APU emulator, designed by myself and my partner from the ground up. Original versions of Silhouette also included an encryption scheme to prevent customers from hacking the software and using ROM images other than the game included with the emulator; the version you have does not include this encryption, however.
An interesting note is that most employees at Nintendo had no idea that other people had already thought of SNES emulation until very recently. The entire SNES9X cancellation story is a huge mess of bad PR for Nintendo, but it couldn't be helped--if a Super Nintendo emulator were released as freeware (along with the heavy ROM piracy that is characteristic of the Internet), the market for Silhouette would be slim to none. Nintendo's efforts in combatting ROM image piracy have always been swift and effective, and frankly I feel nothing but satisfaction seeing ROM pirates get shut down. Try watching your colleague's or friend's hours and hours of labor get translated into a ZIP file and get spread across the Internet and see how it makes you feel. Piracy sucks, people--don't use Silhouette as a vehicle for piracy.