Linux-kernel mailing list archive 2000-15,: Re: Little(?) PCI problem

# Re: Little(?) PCI problem

Martin Mares (mj@suse.cz)
Sun, 9 Apr 2000 21:13:24 +0200

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Hello!

> Is there a way to _disable_ a PCI card's bus master capability?
> I ask this because my brand new BP6 mainboard documentation
> says that PCI slots 4 and 5 share the same bus master signal
> and I cannot fill all 5 PCI slots and have all cards working.
> Here's my machine setup:
>
> AGP videocard, shares IRQ with 1st PCI slot
> 1st PCI: Hollywood Plus DVD decoder
> 2nd PCI: SB Live!, does not share IRQ with other slots
> 3rd PCI: Bt878 TV card, shares IRQ with the onboard HPT366
> 4th PCI: presently nothing in it, shares IRQ and
> bus master signal with 5th slot
> 5th PCI: Symbios 53C875J SCSI card (Diamond Fireport 40)
>
> And I also have a 3Com 3c905B which I would like to use.

Bus mastering can be disabled (bit 2 in the command register), but
it's highly improbable that the card will continue working then :-)

Older 3Com PIC NIC chips support both bus mastering and old-fashioned
packet transfers using MMIO and the Linux driver supports both of them
(actually, it needs to do so as many revisions have the bus master mode
extremely buggy), but according to the comments at the start of the
3c59x driver, starting with the B revision, 3c90x cards work only
in the bus master mode.

Probably the wisest thing you can do is to get a motherboard with real
PCI BUS.

Have a nice fortnight

    --
    Martin `MJ' Mares <mj@ucw.cz> <mj@suse.cz> http://atrey.karlin.mff.cuni.cz/~mj/
    "Don't take life too seriously -- you'll never get out of it alive."

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