Isn't the IT8888 configured in some transparent mode where it masks itself like intel PCI2ISA bridge? Look at full PCI devices listing if you find some...

hpxca wrote on 2026-02-11, 23:24:

Edit: I guess it's because it's the older ITE8888F instead of the newer ITE8888G. Might still work since as best I can tell they are very similar, but the current program doesn't recognize it.

The F and G variants appear to be the same chip with a different package, so there is likely something else stopping it from working

Yeah, it's somehow hidden or lying. I tried PCICFG and pcisleep under DOS. Both list everything you'd expect including the usb controller and Ethernet controllers (when they're enabled). But the IT8888F isn't listed. There is however an Intel PCI to ISA bridge listed. So if that's not actually the chipset then that must be it.

hpxca wrote on Yesterday, 04:14:

Yeah, it's somehow hidden or lying. I tried PCICFG and pcisleep under DOS. Both list everything you'd expect including the usb controller and Ethernet controllers (when they're enabled). But the IT8888F isn't listed. There is however an Intel PCI to ISA bridge listed. So if that's not actually the chipset then that must be it.

The Intel PCI to ISA bridge would be the the LPC interface on the ICH4 southbridge which is used to connect to the Winbond Super I/O chip

So my knowledge of how PCI works is pretty limited, but the AI has been teaching me a lot. Digging through the datasheet of the IT8888F I can't find anything that suggests it can hide itself intentionally, like a setting in a configuration register or a strapping resistor. It does support subtractive decode though and I think that's probably what's going on here. Given this is an ICH4 southbridge I kind of expected DMA to just work and as @KYA mentioned in the original post the ICH4 supports PPDMA so why wouldn't it just use that? I wondering if maybe the BIOS just isn't configuring it properly? The chip supports configuration via an external serial EEPROM as well, but I see no such EEPROM anywhere on the board around the chip so I assume that the BIOS is setting up the registers at boot. I even dumped the BIOS of this board and put it into modbin6 to see if there was something hidden in there that might be related to it, but nothing stood out. I can't find any other versions of the BIOS for this board anywhere.

With some AI help I might try a few things to play with the configuration registers and see if I can somehow "turn on" PPDMA? But i'm not sure I can make it appear on the BUS so that KYAs program can find it, though I may be able to write something that can detect it anyway...

hpxca wrote on Yesterday, 04:14:

Yeah, it's somehow hidden or lying.

ICH settings usually hide PCI-ISA bridge (IT8888) to avoid conflicts.
You need to search ICH datasheet for something like this.

Ah yes, it should be like this. So to check and clear bit 24. But it seems also this feature is depending on HW configuration - if Ad22 line is routed to ITE as described...

Thanks guys, I installed Open Watcom v2 on my K6-2 and with a little help from Gemini wrote a simple C program with DOS32/A to read and modify bit 24 in the GEN_CNTL register of the ICH4. This worked to unhide the ITE PCI to ISA bridge on that Pentium 4 board which was on Bus 2 Device 6. With this done the itexxx.exe had no issue finding it and configuring it for DDMA. Unfortunately, this is where the good news ends. I tried two low-end Vibra16 sound cards, the really, really low-end CT4170 which really has no 16-bit DMA at all (the pins aren't even there on the ISA connector, so high DMA = low) and the CT4180 on which high DMA works. I tried both DMA 1 and 3 for low, and 5 for high on the CT4180. In all cases, as soon as any attempt to do DMA takes place the system just locks up. This happens in the SB "diagnose.exe" when it tries to test DMA and when doom is started after it tries to initialize the sound.

Notably, in the datasheet above bit 25 seems to be there to switch the PPDMA request/grant pair. As a separate little project, I also tried to set bit 25 (without the PCI/ISA bridge unhidden) and checked that the pins(s) were not being used for GPIO in GPIO_USE_SEL as the datasheet recommends. Everything in the PCI_DMA_CFG register suggests that the board is all setup to do PC/PCI DMA (as opposed to DDMA), but despite trying both pairs DMA still doesn't work.

It was a fun little project and I learned a lot about PCI in the process, but it's a shame that boards ISA slots remain DMA-less.

Did you run VDMA8 driver as described in the 1st post?

I did yes right after itexxx.exe, it ran, did its thing (stayed resident I assume) and returned me to the command prompt, then I ran the game (doom) or diagnose. Doom locks up at sound init, diagnose got through the base address, midi address and IRQ and then the system locks up at the DMA test.