NAME

cg − Interphase Cougar VMEbus SCSI Controller

DESCRIPTION

The Interphase Cougar dual-port SCSI controller is a 6U-style VMEbus controller capable of handling two independent SCSI busses.  The Cougar controller supports both SCSI-1 and SCSI-2 devices and provides speeds up to 10mb per second with appropriate devices.  The Cougar board handles all details of the SCSI interface including device selection, command transmission, data transmission, message transmission, and disconnection and reconnection of target devices on the SCSI bus.  The CPU is only notified via interrupts when commands are completed.  The Cougar handles data chaining to host memory (scatter-gather) via DMA and  multiple command queueing. 

Each Cougar controller can have either one or two independent SCSI bus connections.  The primary SCSI bus is always available.  The secondary bus is available as an option via a daughter card which plugs onto the standard controller. 

The cg interface module was designed to be compatible with the hs and is interface modules.  Indeed, it supports the same peripheral set and is implemented using many of the same algorithms. As with the HMVE SCSI Adaptor (HSA) and Integral SCSI/Ethernet Daughtercard (ISE), the cg interface module was designed to work with SCSI devices that support the Common Command Set (CCS) extensions to the SCSI-1 standard.  Most disk and tape drive vendors now supply embedded SCSI controllers that support the CCS extensions.  The CCS extensions have also been incorporated into the more recent SCSI-2 standard, implying those devices which support the SCSI-2 standard may work with the is interface module as well.  However, drives not supporting the SCSI-1 standard plus the CCS extensions are not likely to operate correctly with the Cougar interface without some customization of system software. 

While the Cougar controller software has been tested with a wide variety of devices, it has only been extensively tested with the selected devices available directly from Harris.  Because the compatibility testing done with third party SCSI devices is not nearly as complete as the testing that occurs with standard Harris products, Harris does not guarantee that any third party SCSI device will function correctly when connected to the  Cougar interface.  Harris can provide some limited technical assistance to integrators experiencing difficulties with non-Harris devices, however, the variations in third party SCSI hardware are too great to guarantee that all devices will function properly with the Cougar hardware and software.  Cougar Hardware Configuration

The SCSI standard allows for 8 device addresses on the SCSI bus called SCSI bus IDs.  The Cougar controller software can support any combination of up to 7 SCSI target devices per SCSI bus since it must reserve a bus ID for itself.  By convention, SCSI bus ID 7 is reserved for the Cougar interface on each bus and should not be used by any target device.  Also by convention, disk devices are generally assigned first from SCSI bus ID 0 up to SCSI bus ID 6.  Tape devices are generally assigned SCSI bus IDs 5 down to SCSI bus ID 0.  SCSI bus ID 6 is only assigned if all other IDs are already assigned.  The /etc/master system configuration file identifies which bus IDs correspond to which disk/tape units.  An excerpt from a configuration file is included below.  Additional limits of 32 disk units of all types and 16 tape units of all types are imposed by the CX/UX system software. 

The primary SCSI bus on the Cougar is connected to the P3 connector on the front of the controller.  If present, the secondary bus is connected to the P9/J1 connector on the front of the controller daughter card.  Software Configuration

Disk and tape drives connected to the primary SCSI bus on the Cougar are configured as any other disk or tape drive except that the controller name is cg.  However, devices connected to the secondary SCSI bus are identified by having eight (8) added to their SCSI bus ID value.  For example, a tape driver having a SCSI ID of 5 will have its system configuration file drive value set to 13 to indicate that it is on the secondary SCSI bus.  The following excerpt from the /etc/master system configuration file illustrates how to configure the Cougar with two disks on the primary SCSI bus and a single disk and tape drive on the secondary bus. 

 ...
 ...
controllercg0at vba0 csr 0xff2800vector cgintr
 diskdsk0at cg0 drive 0
diskdsk1at cg0 drive 1
diskdsk2at cg0 drive 8
tapemt0at cg0 drive 13
  ...
 ...

CX/UX Device Drivers

Like all disks on a CX/UX system, disks configured on the Cougar SCSI controller are accessed via the Generic Disk driver (gd(7)).  The advantage of this approach is that programs that could interact with potentially many disk device drivers will instead interact with a single common device driver.  This results in a high degree of compatibility for both user and system level software.  The use of a common driver also insures consistency in device naming and numbering conventions and facilitates almost identical system administration procedures such as formatting, partitioning, etc.  Refer to gd(7) for more information about the generic disk driver and its facilities. 

Similarly, all tapes (with the exception of Pertec interface tapes configured on a Xylogics tape controller) use the Generic Tape driver (gt(7)).  Again, user and system level software see a single common driver interface that insures application portability among different tape drives as well as common administration procedures.  Refer to gt(7) for more information about the generic tape driver and its facilities.  Performance

The Cougar SCSI controller can accommodate both synchronous and asynchronous transfer modes on the SCSI bus.  It can achieve transfer rates up to 10 Mbytes/sec or more on the SCSI bus.  However, in practice, the maximum transfer rate of the SCSI target device with which the interface communicates is the maximum achievable transfer rate. 

SEE ALSO

config(1M), master(4), format(1M), hdc(7), ise(7), gd(7), gt(7)

CX/UX Administrator’s Reference