What system disk size limit on the MicroVAX and VAXstation 3100?
System disks larger than 1.073 gigabytes (GB)—1fffff hexidecimal blocks — are not supported on any member of the VAXstation 3100 series and on certain older members of the MicroVAX 3100 series, and are not reliable on these affected systems. (See below to identify the affected systems—the more recent members of the MicroVAX 3100 series systems are NOT affected.) Various of the SCSI commands used by the boot drivers imbedded in the console PROM on all members of the VAXstation 3100 series use “Group 0” commands, which allow a 21 bit block number field, which allows access to the first 1fffff hexidecimal blocks of a disk. Any disk references past 1fffff will wrap—this wrapping behaviour can be of particular interest when writing a system crashdump file, as this can potentially lead to system disk corruptions should any part of the crashdump file be located beyond 1.073 GB. More recent systems and console PROMs use “Group 1” SCSI commands, which allow a 32 bit block number field. T
