To expand on the above, absolute theoretical 16bit ISA limit is 2 cycles per transaction (0WS), (2 Bytes x clock MHz)/2 cycles = ~8MB/s at 8MHz. In practice best period correct VGA cards reach ~4-6MB/s write speed. Slowest VLB cards do ~10MB/s fastest ~30MB/s, slowest PCI VGA ~15MB/s fastest again ~30MB/s.