Stainlesscat wrote on 2021-03-14, 09:33:
Okay i found the actual reason why i can't seem to get any pci sound cards with legacy isa i/o requirements for SB emulation to work on my particular motherboard. i found some info regarding an old mfsn forum post that was informational about mid to late lga 775 motherboards without LPC connected to address the isa resources to the ICH7 southbridge mostly from intel & oem motherboards. which i thought was the main culprit but ironically my Intel motherboard does have an Winbond LPC to PCI chip, but it only supports Super I/O devices like PS/2 Serial and dma only for floppy drives meaning my LPC chip is super limited. Which also means my motherboard does not meet the requirements for legacy ISA port addressing towards the pci bus which is why my sound card doesn't work with Sound Blaster Pro emulation. (See my post above this one for reference)
Most motherboards come with a SuperIO chip connected to LPC, mainly for PS/2, COM or maybe LPT ports. That chip has little use outside its intended purposes. Today SuperIO is only relevant for PS/2 ports and maybe hardware monitoring (temperature, voltages, fan speed, etc.).
Motherboards using LPC-to-ISA (such as RUBY-9719VG2AR) to provide ISA slots can make use of DMA, but one needs to configure the chipset to correctly route necessary I/O ranges to the bridge to make the device accessible. This, however, is not going to be helpful for PCI devices.
Given PCI-to-ISA bridges don't have issues with I/O ranges compared to LPC-to-ISA ones, and that industrial use cases usually don't have extensive use of DMA, ISA motherboards using PCI-to-ISA bridges are more common. LPC-to-ISA bridges can use DMA on chipsets up to Intel 9-series. According to Tiido, DMA-related pins were removed from the LPC bridge on 10-series and onwards such as H110 (EDIT: It appears this was for the transition to the new eSPI).
Stainlesscat wrote on 2021-03-14, 09:33:
For the legacy ports stuff to work, You need a compatible chipset like intel's I/O Controller HUB (ICH Series chipset) or VIA VT8233 or later with a combined LPC to PCI bridge chipset with legacy ISA resources support! a.k.a ISA port mapping and DMA Support, Because without these; you will find similar issues like i or others experienced. So just having a compatible southbridge that support subtractive decoding is not enough!... unless it's like the earlier VIA/SiS chipsets with the LPC or ISA integrated in the chipset.
DDMA-capable southbridges like VT82C686B can make PCI sound cards work with little efforts.
PC-PCI is a different story as it requires physical connections which I'm yet to find any on modern motherboards using chipsets capable of such. For ISA motherboards using ICH5 or earlier, these wires were used to provide DMA-capable ISA slots. I think PC-PCI might be able to provide better legacy compatibility than DDMA, since most of the operations are being performed directly over physical wires.
On modern chipsets these capabilities are gone so it pretty much depends on whether the sound card's own DMA technology can work with a given chipset. VIA/SiS chipsets might be the most cooperative ones in this aspect.
Stainlesscat wrote on 2021-03-14, 09:33:
So i now switched to a gigabyte ga-g31m-es2l motherboard and my yamaha ds-xg works fine with complete & fully functional Sound blaster emulation in both real mode DOS via TSR and Win9x. So for those who want to experience an easy compatible setup for retro dos support on modern lga775 chipsets from the get go, I highly suggest to avoid all intel oem motherboards made after the 865G series as those have crappy LPC to PCI bridges with no legacy support which can't support the ICH chipset's subtractive decoding I/O to PCI. Just stick to a named branded manufacturer as those have fully feature sets to get everything needed to work.
Intel ICH only supported PC-PCI up to ICH5. It cannot be used directly, unless the board is generous enough to have the necessary pins accessible (which I've never seen one) so you can connect your sound card to it.
Intel ICH never supported DDMA. I don't know much about LPC-to-PCI bridges, but I don't think LPC is going to be of any use for PCI devices to access legacy DMA.
Stainlesscat wrote on 2021-03-14, 09:33:
Also an other thing to note is that later lga775 intel motherboards are usually crappy and are usually low quality + have severe BIOS limitations.
If you're talking about industrial LGA775 motherboards, yes, these boards' BIOS usually don't provide anything extra, as industrial use cases are more conservative and favor stability and reliability over anything else.
On the other hand, consumer motherboards have a lot of interesting features, and actually some LGA775 CPU-motherboard combinations can overclock very well, from what I've read before.