Reply 40 of 51, by LSS10999
wrote:could this help with PCI sound cards in DOS? […]
could this help with PCI sound cards in DOS?
ISA enable.This bit modifies the response by the bridge to ISA I/O addresses.This applies only to I/O addresses that are enabled by the I/O base and I/O limit registers and are in the first 64 KB of PCI I/O address space (0000 0000h to 0000 FFFFh). If this bit is set, then the bridge blocks any forwarding from primary to secondary of I/O transactions addressing the last 768 bytes in each 1-KB block. In the opposite direction (secondary to primary), I/O transactions are forwarded if they address the last 768 bytes in each 1K block.
0 = Forward downstream all I/O addresses in the address range defined by the I/O base and I/O limit registers (default)
1 = Forward upstream ISA I/O addresses in the address range defined by the I/O base and I/O limit registers that are in the first 64 KB of PCI I/O address space (top 768 bytes of each 1-KB block)
I think this would only help with operations against ISA I/O ranges so things like FM synth would work, and would not solve the fundamental issue (which is legacy DMA). The chipset is required to have certain capabilities (such as PC-PCI/DDMA) in order to enable uses of legacy DMA channels on PCI devices, which is required for DOS games to have functional SFX. Such capabilities were long gone from modern chipsets, although they may retain LPC DMA capabilities so one can still put a SuperIO (LPC-based) chip which in turn provides legacy ports such as PS/2, LPT and COM(UART). (NB: TPM also utilizes LPC bus for its operations)