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SI(4) Kernel Interfaces Manual SI(4)


si, swNCR 5380 SCSI bus host adaptor driver



si0 at obio0 addr 0x140000 ipl 2

sun3 and sun3x

si0 at vme2 addr 0x200000 ipl 2 vect 0x40
si1 at vme2 addr 0x204000 ipl 2 vect 0x41


sebuf0 at vme2 addr 0x300000 ipl 2 vect 0x74 # and 0x75
sebuf1 at vme2 addr 0x340000 ipl 2 vect 0x76 # and 0x77
si* at sebuf?

sun4 and sun2

si0 at vme0 addr 0x200000 pri 2 vec 0x40


sw0 at obio0 addr 0x0a000000 level 3


The si and sw “SCSI Weird” drivers provide support for the NCR 5380 SCSI Bus Controller (SBC) chip found on various Sun Microsystems CPU motherboards (obio), and on the “Sun-3 VME SCSI” (Sun part # 501-1236) board used in systems with VME bus.

sun3 and sun3x

The sun3 and sun3x version of this driver can be configured with a flags directive in the config(1) file. The values are bits in a bitfield, and are interpreted as follows:

Set bit (1<<target) to disable SCSI disconnect/reselect
Set bit (1<<(target+8)) to disable SCSI parity checking
Set this bit to disable DMA interrupts (poll)
Set this bit to disable DMA entirely (use PIO)

For example: “flags 0x1000f” would disable DMA interrupts, and disable disconnect/reselect for targets 0-3. The “target” is the SCSI ID number of a particular device on a particular SCSI bus.


The sun4 version of this driver can also be configured with a flags directive in the config(1) file. The values are bits in a bitfield, and are interpreted as follows:

Use DMA (may be polled)
Use DMA completion interrupts
Allow SCSI disconnect/reselect

For example: “flags 0x07” would enable DMA, interrupts, and reselect. By default, DMA is enabled in the sun4 driver.


David Jones, Gordon Ross <>, Adam Glass <>, Jason R. Thorpe <>.


The VME variant has a bit to enable or disable the DMA engine, but that bit also gates the interrupt line from the NCR5380 (!!). Therefore, in order to get any interrupt from the NCR5380, (i.e. for reselect) one must clear the DMA engine transfer count and then enable DMA. This has the further complication that you CAN NOT touch the NCR5380 while the DMA enable bit is set, so we have to turn DMA back off before we even look at the NCR5380.

Support for the Sun 4/100 sw “SCSI Weird” is not complete. DMA works, but interrupts (and, thus, reselection) don't for reasons unknown. Further progress has halted pending the availability of a machine for testing.

DMA, DMA completion interrupts, and reselection work fine on a Sun 4/260 with modern SCSI-II disks attached. There have been reports of reselection failing on Sun Shoebox-type configurations where there are multiple non-SCSI devices behind Emulex or Adaptec bridges. These devices pre-date the SCSI-I spec, and might not behave the way the NCR5380 code expects. For this reason, only DMA is enabled by default in the sun4 driver.

May 7, 1998 NetBSD 7.0