NAME

hdc − HVME Disk Controller

DESCRIPTION

The HVME Disk Controller (HDC) is an HVME based disk controller for SMD and SMD/E interfaced disks.  The HDC offloads many disk management functions from the CPU to the controller.  Specifically the HDC provides disk scheduling and data chaining (scatter-gather), flaw management, retries, as well as error recovery.  The HDC controller essentially presents an error free media to the system software, with no CPU intervention required for error recovery, retries, track/sector relocation, etc.  The HDC can support up to four SMD or SMD/E interface disk drives and supports a disk I/O bandwidth of up to 24 mhz at the SMD/E interface.  Hardware Configuration

HDCs are supported on the Harris Enhanced VME bus (HVME).  A system may be configured with as many HDCs as it has available HVME slots, with at most four disk drives per HDC numbered 0-3. The CX/UX generic disk driver gd(7) can support no more than 32 disks OF ANY KIND per kernel configuration.  An HDC identifies whether or not a disk is connected by the presence of a profile prom for each particular drive that is connected to the controller.  Included in the profile prom are model specific parameters and geometry information for a particular disk drive model.  Whenever a new drive is added to an HDC controller, a profile prom must also be added for the drive to recognized.  Whenever a drive model is changed, the profile prom for the old model must be replaced with one for the new model.  However, profile proms do not need to be changed if a drive is to be replaced with a drive that is the same model as the one with which it is currently configured.  Software Configuration

The following excerpt from an /etc/master configuration file illustrates a sample configuration of two HDCs, each with four disk drives.  Note that the controller csr and vba number may be specified or left as ’?’.  In the latter, the system software will probe all addresses corresponding to the valid HDCs in an attempt to locate the HDC.  The search will progress on the primary I/O bus first, from slot 1 to the maximum slot number, and then the secondary I/O addresses will be scanned. 

 ...
 ...
controllerhd0at vba0 csr 0x03vector hdintr
controllerhd1at vba? csr ?vector hdintr
 diskdsk0at hd0 drive 0
diskdsk1at hd0 drive 1
diskdsk2 at hd0 drive 2
diskdsk3 at hd0 drive 3
diskdsk10 at hd1 drive 0
diskdsk11at hd1 drive 1
diskdsk12 at hd1 drive 2
diskdsk13 at hd1 drive 3
 ...
 ...

CX/UX Device Driver

Like all disks on a CX/UX system, disks configured on an HDC will be 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. 

FILES

/hdcwcs  -  HDC downloadable microcode/control store

SEE ALSO

config(1M), master(4), format(1M), gd(7), hsa(7)

CX/UX Administrator’s Reference