Hmm did the board you get have no writing on any of the chips except one like in the picture ?
Not sure about a M 845EG but the DMA works fine on all my soc 478 so far... Does a floppy drive work ? That uses DMA 2. Knowing that might help....
Most BIOS do not let you assign or lock DMA's like you can with IRQ's.

That AliExpress link doesn't work for me. Could you post pics of your specific board. In particular get pics of any non-Intel chips between the southbridge and the ISA slots. Typically a Winbond bridge chip is used, exactly which should tell us what options you do or don't have.

OP's aliexpress link goes to this board for me:

https://www.aliexpress.us/item/2251832778926475.html

https://theretroweb.com/motherboards/s/adlink-m-845eg

Also, not sure how similar it is to this board since the layout is a bit different, but TRW implies that they are related:
https://theretroweb.com/motherboards/s/dfi-g4v620-b

The board layout picture for the DFI board says the Winbond chip is a w83627hf.

Also worth noting, all of these variants seem to say that the AGP slot is actually just an ADD (AGP Digital Display) slot, for use with those basic cards that just provide a DVI output for the onboard video. You can't use a normal AGP video card in these.

Ozzuneoj wrote on 2025-03-10, 07:45:

https://theretroweb.com/motherboards/s/adlink-m-845eg

It seems to be this board. It appears to be using IT8888 for ISA which is a PCI-ISA bridge.

I don't have this board but this issue is probably similar to ANOVO AIMB-865 on which DMA also does not work out-of-box.

If you have tools to access PCI configuration registers you can check registers 90-91h of Bus 0 Device 31 function 0 (0.1f.0).

Check if the bits corresponding to the DMA channel you need to use are set to 01b (PC/PCI) instead of 11b (LPC). In case of using DMA 1 and 5 that would be bits 11:10 and 3:2. If they're set to 11b then this is the problem.

Some boards (which was the case for AIMB-865) default to route all DMA channels to LPC (11b) which would break DMA on sound cards plugged in the ISA slot if a PCI-ISA bridge is used to provide such, and BIOS options such as DMA channel settings do not actually toggle them for correct behavior.

Set only the channels the cards need to 01b and DMA should be working afterwards. This can be done from within DOS. Be sure to leave the bits of other DMA channels untouched or you may break functionality provided by SuperIO (which is on the LPC bus), such as FDD and ECP printer port.

NOTE: The datasheet for ICH4 can be found on TRW which you can find more info about the registers.