bt(4) Buslogic/Mylex MultiMaster SCSI host adapter driver


To compile this driver into the kernel, place the following lines in your kernel configuration file:
device isa device scbus device bt

In /boot/device.hints


This driver provides access to the SCSI bus connected to a Buslogic/Mylex MultiMaster or compatible controller:
MultiMaster "W" Series Host Adapters:

Adapter Ta Bus Ta Commands Ta Description BT-948   PCI     192     Ultra SCSI-3
BT-958  PCI     192     Wide Ultra SCSI-3
BT-958D PCI     192     Wide Differential Ultra SCSI-3

MultiMaster "C" Series Host Adapters:

Adapter Ta Bus Ta Commands Ta Description BT-946C  PCI     100     Fast SCSI-2
BT-956C PCI     100     Wide Fast SCSI-2
BT-956CD        PCI     100     Wide Differential Fast SCSI-2
BT-445C VLB     100     Fast SCSI-2
BT-747C EISA    100     Fast SCSI-2
BT-757C EISA    100     Wide Fast SCSI-2
BT-757CD        EISA    100     Wide Differential Fast SCSI-2
BT-545C ISA     50      Fast SCSI-2
BT-540CF        ISA     50      Fast SCSI-2

MultiMaster "S" Series Host Adapters:

Adapter Ta Bus Ta Commands Ta Description BT-445S  VLB     30      Fast SCSI-2
BT-747S EISA    30      Fast SCSI-2
BT-747D EISA    30      Differential Fast SCSI-2
BT-757S EISA    30      Wide Fast SCSI-2
BT-757D EISA    30      Wide Differential Fast SCSI-2
BT-545S ISA     30      Fast SCSI-2
BT-542D ISA     30      Differential Fast SCSI-2
BT-742A EISA    30      SCSI-2 (742A revision H)
BT-542B ISA     30      SCSI-2 (542B revision H)

MultiMaster "A" Series Host Adapters:

Adapter Ta Bus Ta Commands Ta Description BT-742A  EISA    30      SCSI-2 (742A revisions A - G)
BT-542B ISA     30      SCSI-2 (542B revisions A - G)

Tagged queueing is supported on 'W' series adapters, 'C' series adapters with firmware of rev 4.42 and higher, and 'S' series adapters with firmware of rev 3.35 and higher.

Boards with certain firmware revisions may lock up under heavy load to certain devices, especially if tagged queueing is used. Should you encounter a problem with your adapter, contact Mylex technical support and ensure you have the latest firmware for your controller.


The driver supports the following BusLogic MultiMaster ``W'' ``C'' ``S'' and ``A'' series and compatible SCSI host adapters:

  • BusLogic BT-445C
  • BusLogic BT-445S
  • BusLogic BT-540CF
  • BusLogic BT-542B
  • BusLogic BT-542B
  • BusLogic BT-542D
  • BusLogic BT-545C
  • BusLogic BT-545S
  • BusLogic/BusTek BT-640
  • BusLogic BT-742A
  • BusLogic BT-742A
  • BusLogic BT-747C
  • BusLogic BT-747D
  • BusLogic BT-747S
  • BusLogic BT-757C
  • BusLogic BT-757CD
  • BusLogic BT-757D
  • BusLogic BT-757S
  • BusLogic BT-946C
  • BusLogic BT-948
  • BusLogic BT-956C
  • BusLogic BT-956CD
  • BusLogic BT-958
  • BusLogic BT-958D
  • Storage Dimensions SDC3211B / SDC3211F

AMI FastDisk Host Adapters that are true BusLogic MultiMaster clones are also supported by the driver.


The driver first appeared in the BSD 386 patch kit.


An -nosplit An Julian Elischer wrote a driver for the Multimaster cards that appeared in the BSD 386 patch kit. The driver was rewritten by An Justin T. Gibbs to take advantage of new board features and work with the CAM SCSI framework in Fx 3.0 .

Special thanks to An Leonard N. Zubkoff for writing such a complete and well documented Mylex/BusLogic MultiMaster driver for Linux. Support in this driver for the wide range of MultiMaster controllers and firmware revisions, with their otherwise undocumented quirks, would not have been possible without his efforts.