*BSD News Article 74061


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Strange new errors with 32mb upgrade
Date: 17 Jul 1996 20:43:28 GMT
Organization: Private BSD site, Dresden
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emerys@confucius.omniscient.com (Sean Emery) wrote:

(bounce buffers)

> In response, the only ISA card that I have is an 8bit SoundblasterPro.
> I do have a SCSI card, NCR825 PCI.  The 'handbook' is very terse 
> concerning these 'bounce buffers', so if anyone has more insight, I'd 
> be surely thankful for the info or pointer where I can find more info.

You only need it for busmaster DMA controllers on the ISA bus (since
the ISA bus has only 24 address lines, hence can only reach 16 MB of
RAM).  DMA devices working on the (terrible) DMAC on the motherboard
are being automagically bounce-buffered (they need it much more, even
for crossing a 64 KB boundary, since the motherboard DMAC is from the
8080 family and can only address 64 KB directly).

So it really looks like bad RAM.  Since it doesn't crash immediately
but only once you're loading the machine, it's very likely the added
RAM.  (Machine crashes as the RAM above the old 16 MB gets into use.)

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)