*BSD News Article 25120


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From: rkb55989@uxa.cso.uiuc.edu (Rafal Boni)
Newsgroups: comp.os.386bsd.development
Subject: Re: [FreeBSD 1.0R] DMA Problems?
Date: 17 Dec 1993 21:59:15 GMT
Organization: University of Illinois at Urbana
Lines: 53
Message-ID: <2eta3j$6t9@vixen.cso.uiuc.edu>
References: <2eopau$hde@vixen.cso.uiuc.edu> <jmonroyCI6HqF.Hxu@netcom.com>
NNTP-Posting-Host: uxa.cso.uiuc.edu

jmonroy@netcom.com (Jesus Monroy Jr) writes:

>Rafal Boni (rkb55989@uxa.cso.uiuc.edu) wrote:
>: j@uriah.sax.de (J Wunsch) writes:

>: [stuff J"org and Terry were debating deleted...]

>: >In fact, i'm also experiencing lotta DMA overruns when attempting to do
>: >some floppy IO while some heavy compile job is running. This is in a box
>: >with an Adaptec SCSI, and i didn't track it down whether it's the CPU
>: >load that causes the trouble (would really look strange to me), or if
>: >it's the heavy disk IO that happens while compiling.


>: 	I would be tempted to say that the Adaptec is at fault... I have a 
>: 	3Com 3c507 Ethernet card in my machine, and the docs SPECIFICALLY
>: 	mention the fact that Adaptec's 154x may cause problems for the
>: 	Ethernet card's DMA reads/writes....  Later 3Com updated some of
>: 	the [I would guess] DMA related circuitry to be able to handle longer
>: 	timeouts or something of that nature... 
>:
>	Most problems encountered with Adaptec's 154X and ethernet
>	cards are I/O port, IRQ and DMA channel conflicts.

	Jesus, Jesus! Read my post.... It's not a configuration conflict!
	What was happening is that the Adaptec would be stealing the bus for
	too long of a time, thus causing the 3c507's DMA requests to time
	out, overrun, underrun, etc.

	Nothing to do with the card's trampling each others' [DMA or I/O port 
	or IRQ] settings...

>	Both 3Com cards and Adaptec's card are configurable to many
>	setting.  Getting them to conflict is very easy.  I would
>	not be so quick to blame the AHA card.  

	FTP to ftp.3com.com and you too can read 3Com's tech notes on the
	subject...  While it may not be 100% Adaptec's fault [in this case, 
	3Com relaxed their own timing reqirements to allow both of the
	cards to work], it definitely is something that was caused by the
	Adaptec's holding on to the bus for too long...


>-- 
>Jesus Monroy Jr                                          jmonroy@netcom.com
>Zebra Research
>/386BSD/device-drivers /fd /qic /clock /documentation
>___________________________________________________________________________

 ----------------------------------------------------------------------------
Rafal Boni   I'm a student -- nothing I say holds any value!   r-boni@uiuc.edu
	This message has not been endorsed by the Surgeon General, nor
	the University of Illinois.  All opinions are my own, not UIUC's.