Chip RAM can't be 'converted' to fast RAM - it resides on the chip bus whereas fast resides on the CPU bus. The only (somewhat) cheap way to get fast is to buy a suitable PCMCIA card.
Actually, chipmem can be considered as better than fastmem because the chipset can use it and the expected speed increase with real fast RAM is hardly noticeable (except when you run 3/4 bitplane hires graphic and maybe overscan, as has been noted - 16 colors and severe overscan could slow the machine to a crawl - the like is true for extreme blitter usage).
