> I just get a used Adaptec 1540B and want to move my system to
> SCSI. however, just today I heard people in OS/2 community
> talking about this very card having problem because it can't address
> any memory above 16M, so OS/2 will use only < 16M for program, and
> all other above it as swap..
> I just want to know if this thing is true for Linux.. since I
> saw nothing of the sort mentioned in SCSI-HOWTO.
> Thanks a lot!
Actually, this IS mentioned in the Linux docs. It is NOT a problem with the
card, OR SCSI! It is a problem with the ISA bus! It has to do with the fact
that only 24 bits(address) are connected to the card. If the program wants
DMA to access anything above 16MB, FORGET IT! It is simply not possible due
to the fact that you need to use the A16-A31 lines.
SO, since it is a HARDWARE problem, Linux is ALSO susceptible. It ALSO has
a config option to disable memory above 16MB! AHHHH, so THAT is what that
stupid question is for!
Yeah, but Linux also knows how to use bounce buffers where necessary to get
around this problem.