The Vision864 has a 64-bit engine and has an 64-bit external data bus. Vision864 boards have DRAM rather than VRAM. VRAM can be found on Vision964 video cards. Another difference is the maximum supported memory; 1MB to 4MB for the 864 and 1MB to 8MB for the 964. The chip is suitable for both VLB and PCI bus.
Both the Vision864 and Vision964 we're decent performers for DOS and 2D-applications back in 1994 and 1995.