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Date: Fri, 22 May 1998 15:27:47 +0100
From: Karl Pielorz <kpielorz@tdx.co.uk>
Organization: TDX
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To: Ruslan Ermilov <ru@ucb.crimea.ua>
CC: FreeBSD Questions <questions@FreeBSD.ORG>
Subject: Re: Questions about Bus Mastering
References: <19980522154209.A1824@ucb.crimea.ua>
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Ruslan Ermilov wrote:
> 
> Hi!
> 
> Bus mastering...
> 
> What I know about it? This is the PCI technology similar to DMA channels
> on the ISA bus. It allows adapters to control the bus. Thus, they can
> deliver their data directly to RAM, minimizing the workload on the CPU.
> Am I right?

Basically yes...
 
> Questions:
> 
> 1. What existing hardware supports bus mastering: SCSI host adapters,
>    IDE controllers, Network adapters? (examples, please)
> 
> 2. Does FreeBSD support bus mastering and for which hardware?
> 
> Thanks,

You should try the -hardware list for more details... PCI cards can
optionally support bus mastering, e.g. Adaptec 2940's do, and BSD does use
it...

I think the general rule is - if the card does it, the driver probably
does... One of the few exceptions I can think of is things like the Matrox
Mystique, which can apparently be run in bus-mastering on non-busmastering
mode...

Regards,

Karl Pielorz

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