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From: Terry Lambert <terry@lambert.org>
Message-Id: <199701081643.JAA16463@phaeton.artisoft.com>
Subject: Re: Bounce Buffers and CCD
To: SimsS@IBM.Net
Date: Wed, 8 Jan 1997 09:43:32 -0700 (MST)
Cc: Hackers@FreeBSD.ORG, toor@dyson.iquest.net
In-Reply-To: <199701081309.NAA198420@smtp-gw01.ny.us.ibm.net> from "Steve Sims" at Jan 8, 97 08:07:39 am
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> Related point:  I believe it was Terry Lambert that stated in previous
> messages (words to the effect) that "option BOUNCE_BUFFERS" is not *strictly*
> needed; that this functionality is automatically enabled on ISA systems with
> >16Meg and that including "options BOUNCE_BUFFERS" in late-model kernel
> configs only serves to *force* BOUNCE_BUFFERS on ISA systems with =< 16Meg. 
> I don't concur.  Removing "options BOUNCE_BUFFERS" on a 32Meg system will
> page-fault-panic a booting box as quickly as anything else I've ever tried! 
> (Terry, I hope I haven't quoted you out of context, but I'm here to tell ya':
> BOUNCE-BUFFERS is a MANDATORY option for >16M systems, at least on
> 3.0-CURRENT with my mo-bo having PCI, ISA and VESA!)

Then it's not required AND it's broken.  8-(.

Bounce conditions are supposed to be autodetected.

What controller are you using? (PCI/VESA/ISA?)
How many address lines are propagated, if PCI/VESA? (24/32?)

It may be that your motherboard is broken... literally, the config
BOUNCE_BUFFERS option is defined as turning on bouncing in conditions
where it is not supposed to be required according to the hardware
specifications for the busses involved.

If you are using an ISA bus mastering DMA controller, it's supposed
to be handled.  If you are using nything else, it's supposed to be
unnecessary; if you find it necessary for non-ISA hardware, your
motherboard is not standards compliant and you should contact the
manufacturer (and send mail with make/model/revision to the hardware
list maintainers for a "don't anyone else buy one of these" note).


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.