Legacy emulation under DOS Creative/Ensoniq cards will not work on systems that . . a) do not route the PCI SERR# signal to the processor NMI b) have a capacitor between SERR# and ground or between NMI and ground that is too large. Some background is required here. The Creative/Ensoniq PCI cards use the PCI SERR# signal to indicate that someone has accessed a Legacy device register (i.e., Sound Blaster, MPU-401, ). This SERR# signal must generate a processor NMI before the I/O instruction completes so that the Legacy emulation software can perform proper emulation of the trapped I/O event before the processor executes the subsequent instructions. In the event that the SERR# signal is not connected to the NMI input, the software is never notified and cannot perform any Legacy device emulation. In the event that there is a capacitor on the line that is too large, the NMI does not propagate to the processor in time to emulate the I/O before the next processor instruction(s) execute(s). If the I/O event is emulated too late, it may have an adverse effect on the system as it may change the state of processor register al at a time when the processor is not expecting it. They have a choice to not wire it to the CPU. They have a choice not to wire SERR# to the southbridge. They have a choice not to enable SERR# NMIs in the southbridge's configuration registers. They have a choice not to provide an NMI handler in the BIOS. They are all sorts of stupid things they can do break NMIs, and something a simple as not wiring a pin can make the difference as to whether another expensive layer on the motherboard is needed. Most motherboards don't support two floppy drives anymore because it means having one less pin to wire that way