I was considering buying a new Pentium-based PC to run NetBSD but I
decided that my current 486-based system is actually quite useful and
replacing it may be overkill (as well as very expensive).  I think my
biggest beef with it is that I'm restricted to 16Mb of RAM.  It's not
unusual for me to be using 25+Mb of swap and the system can slow down
quite a bit as it thrashes through memory pages.

My understanding of the 16Mb RAM limit is the inability of ISA cards
to do DMA transfers to RAM at addresses above 16Mb.  My system has
a 4-port serial card, a SoundBlaster card, a 1542-compatible SCSI
controller (a BT542), and a #9GXE Pro video card.  I believe that the
only one of those cards that does DMA transfers is the SCSI controller.

I was thinking that if I bought a VLB SCSI controller, like the
BusLogic BT445, I would be free to add another 16Mb of RAM and have
no problem.  The only other considerations are the floppy drive and
the IDE hard drive that I have.  My understanding of the floppy
driver is that it implements bounce buffers so it shouldn't be a
problem.  My understanding of the IDE hard disk controller is that
it doesn't even do DMA.  In any case, my IDE hard drive is mostly
DOS and being able to access it from NetBSD is nice, but not
necessary.

So, I buy a BT445 and another 16Mb of RAM and I live happily ever
after without having to put out for a whole new system.  Does anyone
see a problem with this idea?

A couple of other questions:  Would a BT445 be configured as ahb0
or bt0?  Should I consider another VLB SCSI controller that is
supported by NetBSD and would allow me to run 32Mb of RAM?

TIA for any help!

Jan
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Jan Morales                             Department of Computer Science
E-mail: morales@cs.umd.edu                      University of Maryland
URL: http://www.cs.umd.edu/~morales     College Park, MD 20742, U.S.A.