I don't know - the machine I played with it on was a 16MHz 386, and the IFS software was not optimized. But it was way slower than DCT-based JPEGs to compress.

The odd thing about it though, was that it could upscale smoothly. A 320x200 source could be decompressed at 640x400, and it would sort of intelligently "fill in the gaps" on textures etc.