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MicroVAX 3100 M20e

Hardware summary

Nickname:	Teammate II

Cpu:		KA41-D, CVAX+ (60ns), 1KB on chip cache
Vup:		3.5
Tps:		22 (Maybe 30?)

Bus:		SCSI

Memory on CPU:	4 MB
Max. Memory:	32 MB (obtained by piggy-backing MS42-CA and MS42_BA together)
Mem. Slots:	1
4 MB part:	MS42-AB
8 MB part:	MS42-KA
12 MB part:	MS42-BA
16 MB part:	MS42-CA

Max. Disk Size:	1.073 GB

Enclosure:	BA42-B

Notes: MicroVAX 3100 M10e used same hardware in a smaller BA42-A box. On board NCR-5380 SCSI-1, where video is on VAXstation 3100 M38. Can switch EPROM to get VAXserver 3100 KA41-E. Ethernet 'lance' (le0) AMD7990/DC80AMD7992. No video hardware.

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.

There was a similar limitation among the oldest of the MicroVAX 3100 series, but a console boot PROM was phased into production and was made available for field retrofits—this PROM upgrade allows the use of the “Group 1” SCSI commands, and thus larger system disks. There was no similar PROM upgrade for the VAXstation 3100 series.

Systems that are affected by this limit:

  • VAXstation 3100 series, all members. No PROM upgrade is available.
  • MicroVAX 3100 models 10 and 20. No PROM upgrade is available.
  • MicroVAX 3100 models 10e and 20e. Only systems with console VMB versions prior to V6.4 are affected. A PROM upgrade for these specific systems is (or was once) available.

MicroVAX, VAXstation and VAXserver 3100 family

One of the last VAX-series, and the naming conventions went crazy: several MicroVAX and VAXstation models have the 3100 number, and sometimes it's not easy to tell them apart. They are microprocessor-based systems with SCSI strorage elements. A MicroVAX 3100 is a multiuser machine, a VAXstation 3100 is a graphical workstation, while the VAXserver is a MicroVAX 3100 with a single-interactive-user OS license (e.g. fileservers). There's also the Infoserver 100 and 150, which are MicroVAX 3100's designed for servicing CDROM's, tapes and disks to network cliens (this is useful for remote booting or OS install over the network).

The first 3100 was the MicroVAX/VAXstation 3100 Model 10 and Model 20 with the KA440 processor, and with a performance of 3 VUPs.

tips/vax/microvax3100.txt · Last modified: 2010/01/20 10:19 by mattieu