It turns out modifying code is not needed at all. The only thing that is needed is to configure SeaBIOS with CONFIG_ATA_DMA=y.
So the steps needed to make QNX 4 work on current QEMU are
1. Download SeaBIOS source and make sure the configuration has CONFIG_ATA_DMA=y set
2. Build SeaBIOS
3. Run qemu such as "qemu-system-i386 -bios /path/to/seabios/bios.bin -hda qnxdisk ..."
It turns out modifying code is not needed at all. The only thing that is needed is to configure SeaBIOS with CONFIG_ATA_DMA=y.
So the steps needed to make QNX 4 work on current QEMU are seabios/ bios.bin -hda qnxdisk ..."
1. Download SeaBIOS source and make sure the configuration has CONFIG_ATA_DMA=y set
2. Build SeaBIOS
3. Run qemu such as "qemu-system-i386 -bios /path/to/