PCI Bus SHaring I/O with Direct Memry Access Bad?

[Sirrion]

Was having some memory trouble and sound trouble with Warcraft 3 and QUake3, was wondering if its possible that my PCI Bus and Direct Memory Access Controller are sharing the same I/O if that would affect anything? Seeing as my soundcard is PCI and i'm having memory errors? ALso does it hurt that my GefOrce 3 is sharing the same Memory Address and I/O port with my Intel AGP Controller or PCI BUs Memory Address? THey seem to be the same.. If anyone understands this question and could answer it for me i'd appreciate that. THanks.

-Justin

 

[JustinLerner]

Normally only ISA devices will use DMA, not PCI devices. IDE controllers are on the ISA bus, so they can use DMA, but not usually AGP cards or PCI cards. If PCI devices used DMA, they would use only one of the DMA's typically used for soundcards, either DMA 0,1,or 3, since 2 is reserved for floppies and 4 is reserved by the system to access DMAs from 5-7.

Depending upon how old your motherboard is you might have either or neither of the following options in BIOS.
In the BIOS there may be the option to set the DMAx type to ISA, PC/PCI or distributed. Always set DMA 2 and 4 to ISA, then set the other DMA's to PC/PCI if your soundcard is PCI and using DMA's. DMA's when used dynamically are assigned in a roundrobbin fashion by the DMA controller starting at the low number and going up except for DMA 2 and 4, which as stated are reserved. If you have BOTH ISA and PCI devices contending for DMA's, then some DMA's must be set to ISA and others to PC/PCI OR just set to distributed, which allows the controller to decide in a round robbin fashion the next DMA address in succession. So I might set the lower DMA's to ISA and the higher DMA's to PC/PCI or set to distributed.

On newer boards, the DMA type can be set to LPC DMA or PC/PCI types. LPC (low pin count) devices like serial, USB, mouse (AT or PS/2), keyboard (AT or PS/2 ), printer port, etc, all share the same bandwidth of a simulated ISA bus called an LPC bus. If you have this newer type board, set the DMA types to LPC unless you have a PCI device that needs DMA. In this case, set a couple of DMA's like 5-7 to PC/PCI or experiment around until your PCI device works best with the right DMA's.

Are you sure the problem is with DMA's? Usually problems are with IRQ's.

 

[JustinLerner]

You don't explain what OS you are using, but my guess is Windows 9x. Normally, you can force these overlaps by 'manual' or forced installation of devices in 9x.

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Once a device is manually installed in Windows 95, you may have much more difficulty removing or deleting the drivers and objects for the device. Only manually install for non-PnP cards. What I mean by manual, is when the system doesn't detect the device through PnP as a new device.