Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!mips!sgi!cdp!steve
From: steve@cdp.UUCP
Newsgroups: comp.unix.i386
Subject: > 16MB on ISA bus, with aha1542a
Message-ID: <654400008@cdp>
Date: 11 Jul 90 00:50:00 GMT
Lines: 33
Nf-ID: #N:cdp:654400008:000:973
Nf-From: cdp.UUCP!steve    Jul 10 17:50:00 1990


Hi.

I am trying to run over 16MB on an ISA bus machine
(that holds 24MB).  We use an adaptek aha1542a SCSI
controller, and realize that it cannot DMA into
memory over 16MB.

I heard in this group of some parameters in the AT&T
UNIX kernel "3.2...", that allocate kernel buffers
to be used for DMA, when there is a request to DMA
into memory in certain ranges.  Presumably, any
3.2.* UNIX that has these parameters, is capable of
disallowing DMA to memory over 16MB.  The parameters
are called DMAEXCL and DMAABLEBUF.

I am running Interactive 2.0.2, and it doesn't have
DMAABLEBUF.  I wonder if the new release (2.0.2)
does.  Can anyone running 2.2 tell me.  You could
just do : 

     egrep DMA /etc/conf/cf.d/*tune

and post/mail the results.

I have heard that this functionality was added in
AT&T release 3.2.2, so if Interactive's porting base
was 3.2.2, those parameters should be there.


Steve Fram
Community Data Processing (CdP)
{pyramid, hplabs, ...}!cdp!steve