*BSD News Article 30868


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From: soulard@alix.inria.fr (Herve Soulard)
Newsgroups: comp.os.linux.misc,comp.os.linux.development,comp.os.386bsd.development,comp.os.386bsd.questions,comp.sys.ibm.pc.hardware.systems,comp.sys.ibm.pc.hardware.storage,comp.sys.ibm.pc.hardware.misc,comp.periphs.scsi
Subject: Re: BusLogi 445S and DMA Channel (ANSWERS)
Date: 24 May 1994 06:06:57 GMT
Organization: INRIA
Lines: 38
Distribution: world
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References: <2rnjgs$g1l@news-rocq.inria.fr>
Reply-To: soulard@sor.inria.fr
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Keywords: scsi buslogic bt445s

> The SCSI card works fine with DOS and with Linux 1.1.11. The
> only problem is that the DMA channel is not set.

I want to thanks everybody for their answers. The solution is to 
set the swicth 10 in SB2 to OFF. I've also found this information
in a file reporting problems for the BT445S; the problem was not
with DMA chanel but the info was there !

> From /sys/i386/isa/bt742a.c in FreeBSD file KNOWNBUGS
> .....
> Also note that certain revisions of the Buslogic board (Revision C or 
> earlier, firmware revision <3.37) will cause DRRUPTION with systems 
> containing more than 16MB of memory.

For those who may doubt, with my system (20Mbytes and firmware 3.37) it 
works perfectly. I thing my board is revision E.

> The Buslogic BT-445S and the BT-74[27] don't use on-board DMA, which is
> slow; they use busmastering.  So don't worry that it's not using any DMA
> channel, it's not supposed to.

This is an interesting point. But the problem arises with NetBSD-0.9 
that needs the DMA channel. Linux and DOS don't care. I've not tried with
NetBSD-current nor FreeBSD (It seems that FreeBSD does not care). 


Conclusion:

	It is possible to use the DMA channel by unsetting the switch 10,
	but this should not be used, especially if you have more than
	16M bytes of memory.
	
	Bus mastering is better, so use a system that supports it. DOS,
	Linux and FreeBSD work fine with Bus mastering, NetBSD-0.9 requires
	DMA channel.


			Herve Soulard.