Subject: aha 1542: DMA beyond end of ISA
To: None <port-i386@NetBSD.ORG>
From: David Mazieres <>
List: port-i386
Date: 09/16/1995 20:59:06
I am running a very current NetBSD-current on an ISA system with
32Megs of RAM and an Ateptek 1542B SCSI controller.  If I don't change
machdep.c to pretend I only have 16 Megs of RAM, I get a "DMA beyond
end of ISA" message after running for a while (though it lasts a
pretty long time even with X windows and multiple emacses).

I am puzzled since isadma.c appears to check the range of all ISA DMA
transfers and move them to bounce buffers when they are out of range.
Is this a know problem?  Can someone give me a hint as to why this is
happening and what I would need to do to fix the problem?  Presumably
there's either something fundamentally tricky about the Adaptek, or
there's a quick and dirty fix possible that just hasn't been included
in NetBSD because it's 386 specific.  If the latter, I'd at least like
to make a quick and dirty fix to my kernel...

Thanks a lot,