EISA and ISA for SCSI DMA

David L. Oppenheimer (davido@CS.Princeton.EDU)
Sun, 27 Apr 1997 13:17:09 -0400

>From what I've read, ISA SCSI cards can do DMA only into memory
addresses < 16 MB, while EISA SCSI cards do not have this restriction.
In Linux 2.0.24, file drivers/scsi/sd.h, ISA_DMA_THRESHOLD is
#defined to 16 MB, and this is used in sd.c, which makes it apply
to _all_ SCSI cards, including non-ISA cards.

Why is this? Or am I missing something here?

Thanks for any information.